Sorry for the questions, but: 1. Which instructions did you follow? 2. Do you have any add-ons enabled in your browser? 3. Can you tell any difference that happened on 8/4 or shortly before to Firefox (update, ...), your computer (Windows updates, new version of antivirus (AV) / security software / ...)? 4. Which AV or security software do you use? 5. When does Firefox crash? Immediately after starting, when you open a (specific) page, ...? 6. Have you tried to create a new profile? (Open about:profiles, create a new one and open it in a new browser window - you do not need to close the existing Firefox window for that.)

Regarding your information: 1) I cannot load the page either. 2) It could be that you did not (yet) submit any Crash Report to Mozilla. Therefore, the mentioned folder "submitted" does not exist and Windows cannot find it. Does its parent folder "%APPDATA%\Mozilla\Firefox\Crash Reports" exist? 3) How many Firefox processes to you see (I suppose, in the Windows Task Manager)? And which one do you close to open a new window?

Note that support.mozilla.org/t5/ links are from the (short) time when this forum moved to a Lithium based and such links aren't working anymore.

If you have submitted crash reports, please post the IDs of one or more recent crash reports that start with "bp-".

• bp-xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx

You can find the report ID of recent crash reports on the "Help -> Troubleshooting Information" (about:support) page.

• click the "All Crash Reports" button on this page to open the about:crashes page and see all crash reports.

Alternatively you can open about:crashes via the location/address bar.

See also:

• https://support.mozilla.org/en-US/kb/Firefox+crashes

If you can't start Firefox, see: How to get the crash ID if Firefox crashes on startup

• https://developer.mozilla.org/en-US/How_to_get_a_stacktrace_for_a_bug_report

The crash reporter article is https://support.mozilla.org/en-US/kb/mozillacrashreporter

1. Which instructions did you follow? - I attempted to find the crash report, but according to the instructions, it doesn't exist. Firefox isn't crashing. It simply refuses to open, stating that another copy is running, when it is not.

2. Do you have any add-ons enabled in your browser? Yes. Norton 360, adblocker. Note that this exact configuration is running on 3 other Windows 10 computers without issues.

3. Can you tell any difference that happened on 8/4 or shortly before to Firefox (update, ...), your computer (Windows updates, new version of antivirus (AV) / security software / ...)? Nothing occurred out of the ordinary. 4. Which AV or security software do you use? Norton 360 5. When does Firefox crash? Immediately after starting, when you open a (specific) page, ...? It doesn't crash. it never opens, stating that another version is running. 6. Have you tried to create a new profile? (Open about:profiles, create a new one and open it in a new browser window - you do not need to close the existing Firefox window for that.) This is impossible. I cannot get Firefox to open. How many times must I tell you that the only message I get is: an older version is open?

Regarding your information: 1) I cannot load the page either. Firefox never opens with a page. I just get the error window 2) It could be that you did not (yet) submit any Crash Report to Mozilla. Therefore, the mentioned folder "submitted" does not exist and Windows cannot find it. Does its parent folder "%APPDATA%\Mozilla\Firefox\Crash Reports" exist? Since Firefox doesn't crash (It just doesn't open) No crash reports are generated. Ergo, no crash report folder is created.

3) How many Firefox processes to you see (I suppose, in the Windows Task Manager)? And which one do you close to open a new window? If I click the 'close' tab, another Firefox process starts with the same message. If I do this 10 times, I get 10 processes. If I cancel the first one, all Firefox processes terminate.