Try dragging the link you want to open up and dropping it on the address bar as a quick way to open it in the same tab.

However, the cookie jar usually is shared across tabs, so the whole situation is very puzzling.

What if you click in the address bar on the mail tab and press Alt+Enter to re-launch that URL in a new tab. Is the Inbox still logged in?

Have you modified any settings in about:config related to security or privacy? I'm thinking in particular of "first-party isolation" features which might treat proton.com and mail.proton.com as different contexts. I haven't tested that thought.

Try dragging the link you want to open up and dropping it on the address bar as a quick way to open it in the same tab.

Good thought: sadly, it doesn't work. The new link opens not-logged-in.

What if you click in the address bar on the mail tab and press Alt+Enter to re-launch that URL in a new tab. Is the Inbox still logged in?

Nope.

Have you modified any settings in about:config related to security or privacy? I'm thinking in particular of "first-party isolation" features which might treat proton.com and mail.proton.com as different contexts. I haven't tested that thought.

I don't think I've manually changed any 'about:config' parameters at all, ever. Certainly not, recently. I note that looking for 'isolation' in there, 'browser.cache.cache_isolation' is currently set to false. (I have no clue what that means though!)

Many thanks for trying to help, much appreciated.

You are using the Facebook Container extension according to the System Details list.

Is it possible that you have opened thes ProtonMail page in a specific container as that will isolate the cookies from other containers?

• https://support.mozilla.org/en-US/kb/containers

You are using the Facebook Container extension according to the System Details list. Is it possible that you have opened thes ProtonMail page in a specific container as that will isolate the cookies from other containers?

• https://support.mozilla.org/en-US/kb/containers

Hi cor-el, thanks for your input!

I've previously tried disabling all extensions. That didn't help. I've just now visited about:addons, disabled Facebook Container, clicked on the ProtonMail tab with my logged-in inbox, clicked 'help' on that, and it again took me to a new not-logged-in tab at https://protonmail.com/support/. So I've re-enabled Facebook Container.

I have to admit that I don't really understand what 'containers' are all about. I followed your link to try and learn, but it all seemed like gibberish to me. (I trained as a sofware engineer, but it seems to me that the complexity of systems has been accelerating rapidly in recent years. I'm really not looking forward to my dotage...)

... huh? Just posted a reply and I got a message 'A moderator must manually approve your post before it will be visible.' Why?

I'm getting too old for this sh1t.

This is not about the Facebook Container extension, but if you have a container related extension then containers are automatically enabled and it is quite possible that you inadvertently opened this page in a specific container. Using containers isolate cookies from pages opened in a different container. Container are usually identified by a colored bar above the current tab, so you can check what tab-line color you see at the top of the tab if you select the ProtonMail tab and the Proton Help tab.

You aren't using a pinned tab for your Inbox, are you? Pinned tabs aren't suppose to leave the original site, so URLs on other sites need to open in a new tab: Pinned Tabs - keep favorite websites open and just a click away.

This is not about the Facebook Container extension, but if you have a container related extension then containers are automatically enabled and it is quite possible that you inadvertently opened this page in a specific container. Using containers isolate cookies from pages opened in a different container. Container are usually identified by a colored bar above the current tab, so you can check what tab-line color you see at the top of the tab if you select the ProtonMail tab and the Proton Help tab.

Interesting, thanks for the info!

OK, none of the tabs I'm currently using have colored bars above the tab.

I discovered that I could right-click on a tab and select 'reopen tab in container', so I tried that on the (pinned) inbox tab, choosing 'personal'. That opened a new (pinned) tab with a blue line below the icon in the tab. Selecting the proton help link then opened another (non-pinned) tab, at https://protonmail.com/support/ , again with a blue line below -- not logged in. I logged in and: that took me to the inbox again.

You aren't using a pinned tab for your Inbox, are you? Pinned tabs aren't suppose to leave the original site, so URLs on other sites need to open in a new tab: Pinned Tabs - keep favorite websites open and just a click away.

Hi again, jscher! Thanks for sticking with it...

I was using a pinned tab. However, when I unpinned it this made no difference :(

More information:

I restarted in Firefox Safe Mode. Same problem.

I refreshed Firefox. Same problem.

[ Aside: Interestingly, after restoring tabs after the refresh, some of the pinned tabs were logged in to their respective sites, others weren't -- even though I had long ago set 'Ask to save logins and passwords for web sites' off under Options > Privacy & Security > Logins and Passwords. Logged in: Gmail, WordPress, bitly, Pocket, Twitter, F-Droid, Mozilla Support Logged out: Outlook, Discord, Sync.com ]

Troubleshoot and diagnose Firefox problems suggests 6 numbered steps, plus 'other':

(1) I've done numerous times since first encountering this problem. (2) I hadn't yet tried. Did so, clearing everything. Interestingly, this logged me out of some of the other logged in tabs (Gmail, WordPress, bitly, Pocket, F-Droid, Mozilla Support) -- but NOT Twitter. Very odd. Having done so, I tested ProtonMail again... Same problem. (3) I did not long ago. Same problem. (4) Hmm... haven't done that yet. Sounds drastic. (5) I did not long ago. Same problem. (6) Haven't done that yet. (other) Haven't looked at any of these, as yet. Incidentally, I've been using AVG antivirus for years, but recently ditched it in favour of Malwarebytes (as I'd finally had enough of AVG's constant intrusive nagging for more money -- even when on a subscription.)

OK, I'm about to try (4) -- and then move on to 'other' if that doesn't work but will post this first, just in case it does happen to shed any light on wth is going on here.

Back... I did 4. Reinstall Firefox. At the same time I also checked my hard disks for 'Firefox' and deleted any obviously old stuff (going back to 2014).

Reinstalled Firefox (same version as before, latest, ie 84.0.2 (64-bit)).

First thing I did before anything else was check whether this had fixed the ProtonMail problem. It hadn't :(

I'm currently reconfiguring stuff, add-ons and so on, after which I may try 6. Create a new Firefox profile. Then again, I may not. I'm beginning to suspect that this is a ProtonMail issue rather than a browser one, although it's unlikely that I'm the first to encounter it. (I have sent a support request to ProtonMail (via their support form, which, thankfully, doesn't need a log in!). Though it feels like a week ago, I only did that yesterday. I've only had an autoresponse to say there may be a delay as I'm on the free plan. Entirely understandable. And my guess is that I'm not the only one who's been looking at ProtonMail in the last few days, due to the Facebook/ WhatsApp privacy policy change thing, so I bet they're busier than usual anyway. All of which is pretty irrelevant to the matter at hand: I apologise for rambling!)

Just in case it's relevant: although I'd logged into ProtonMail as my very first action after this new installation, I now notice that, having changed some config options and reinstalled three add-ons (DuckDuckGo Privacy Essentials, AdBlocker Ultimate and Facebook Container), I've now been logged out of ProtonMail -- I'm guessing that's to do with the 'container' auto-enablement cor-el mentioned earlier:

This is not about the Facebook Container extension, but if you have a container related extension then containers are automatically enabled[...]

I'm in no particular rush to sort this -- I've had this ProtonMail account for six years, and have barely used it. I can wait some more. But very much appreciate your thoughts if you have any ideas where the problem might be.

Ho hum... I just heard back from ProtonMail. It turns out the only problem is the one in my own head: the 'LOG IN' button on the Proton 'support' and 'blog' pages are intended to allow you to log in to ProtonMail. In my defense, I assumed that they facilitated logging in to some different services within the Proton umbrella because I was already logged in to ProtonMail (and got to those pages with the LOG IN button on them from there)....

I've given them feedback to suggest that, while it's possible that I'm the only klutz on the planet whose brain works this way, perhaps they ought to consider a slight redesign to make it clearer that that LOG IN button is intended to allow you to log in to ProtonMail, just in case there are others who suffer from the same misapprehension as me. Hmm... maybe they should just not show the LOG IN and SIGN UP buttons if you're already logged in? Not sure if that's possible /shrug

Anyway... assuming you're still here: thought I'd post a follow up to clarify -- and to say thanks to jscher2000 and cor-el for trying to assist me with my problem. On the plus side: I've learned a lot about Firefox in the last few days!