Some problems occur when your Internet security program was set to trust the previous version of Firefox, but no longer recognizes your updated version as trusted. Now how to fix the problem: To allow Firefox to connect to the Internet again;

• Make sure your Internet security software is up-to-date (i.e. you are running the latest version).
• Remove Firefox from your program's list of trusted or recognized programs. For detailed instructions, see

Configure firewalls so that Firefox can access the Internet. {web link}

Start Firefox in Safe Mode {web link} by holding down the <Shift> (Mac=Options) key, and then starting Firefox.

A small dialog should appear. Click Start In Safe Mode (not Refresh). Is the problem still there?

https://support.mozilla.org/en-US/kb/what-does-your-connection-is-not-secure-mean

This appears for every website;

https://support.mozilla.org/en-US/kb/what-does-your-connection-is-not-secure-mean

followed the instructions on the link and restarted machine which took ages and still same problem showing

Chez301 said

every page either freezes and crashes Firefox

In the address bar, type about:crashes<enter>. Note: If any reports do not have BP- in front of the numbers/letters, click it to submit them.

The crash report is several pages of data. We need the report numbers to see the whole report.

Using your mouse, mark the most recent 7 - 10 crash reports, and copy them. Now go to the reply box and paste them in.

For more help on crash reports, see; https://support.mozilla.org/en-US/kb/firefox-crashes-asking-support

200ba9cc-bbbd-4cdd-9fd1-5e4fc9d01e65 10/05/2018 09:57 74bfa522-633d-46e8-ad56-979f801d4035 06/01/2018 10:55 c5220873-b28e-4a1b-baab-9d5e5afddefe 06/01/2018 10:55 962e836f-28f2-40ac-87a3-e0c659eab2f6 21/12/2017 23:28 63736e33-1add-44ab-93a8-cd07bc850d28 21/12/2017 10:21 e02b22f0-d9ad-49fa-9505-f60bc57c26e2 02/12/2017 21:51 cea7f0fa-c2dd-4a30-962d-e90962747b93 02/12/2017 20:54 17db9f91-19a8-49e9-93ff-9170e74e0cb5 01/08/2017 12:57

I think this is what you were wanting?

FredMcD said

Note: If any reports do not have BP- in front of
the numbers/letters, click it to submit them.

I've done that

Please post the bp- so we can look them up.