Interesting. Very interesting.

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?

1. In the address bar, type about:config and press the Enter key.
2. The about:config "This might void your warranty!" warning page may appear.
   Click I accept the risk! to continue to the about:config page.
3. Search for the preference security.tls.version.max and set it to 4

FredMcD said

Interesting. Very interesting. 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?

Yes. the problem is still thereTyDraniu said

1. In the address bar, type about:config and press the Enter key.
2. The about:config "This might void your warranty!" warning page may appear.
   Click I accept the risk! to continue to the about:config page.
3. Search for the preference security.tls.version.max and set it to 4

TyDraniu said

1. In the address bar, type about:config and press the Enter key.
2. The about:config "This might void your warranty!" warning page may appear.
   Click I accept the risk! to continue to the about:config page.
3. Search for the preference security.tls.version.max and set it to 4

The problem is still there.

What does it say on the "Tools -> Page Info -> Security" about the connection?

You can also check the connection details in the Network Monitor for the main page (html) on the security tab.

• https://developer.mozilla.org/en/Tools/Network_Monitor

Use "Ctrl+F5" or "Ctrl+Shift+R" to reload the page and bypass the cache to generate a fresh log.

http://kb.mozillazine.org/Security.tls.version.*

This article does not show what setting 4 is. What does it do?

1 means TLS 1.0; 2 means TLS 1.1; 3 means TLS 1.2; 4 means TLS 1.3;

TLS 1.3 is still not considered ready to be enabled in current releases:

Bug 1385927 - Disable TLS 1.3 by default for FF 55
Bug 1387428 - Disable TLS 1.3 by default for FF 56
Bug 1400291 - Disable TLS 1.3 by default for FF 57