see this answer:

• https://support.mozilla.org/en-US/questions/1206972#answer-1082471

Thanks for the responses however none of the suggestions solved the problem. In addition to trying suggested solutions, again tried to disable ESET and Windows Defender without effect. Now using EI which appears to be immune to the root cause problem.

mickbee said

Thanks for the responses however none of the suggestions solved the problem. In addition to trying suggested solutions, again tried to disable ESET and Windows Defender without effect. Now using EI which appears to be immune to the root cause problem.

Why disable ESET when that would not fix anything in this case.

See https://support.mozilla.org/en-US/kb/secure-connection-failed-error-message#w_eset-and-nod32-security-products

Hello, Press Ctrl-Shift-Delete in the Time range select everything Be sure that Active Login is checked Select clear now PS be sure that you have exported all your password https://github.com/kspearrin/ff-password-exporter Happy Sunday!

James,

I'm shooting in the dark. Although I believe I did it previously, I tried disabling ESET again as a troubleshooting measure to be doubly sure it is not at the root of the problem.

Anna,

I tried the steps that you laid out but did not perform the export password step as I'm unfamiliar with what password(s) are exported, to where they are exported, or why passwords would need to be exported. Without more information, exporting passwords seems dangerous.

Thanks for your responses James and Anna, Best Regards, Mike

I previously read an article regarding this problem that suggested renaming or deleting the CERT8 file to resolve the problem however I could not find the file path to this file. I found a UTube video that showed the path and renamed both CERT8 and CERT9. Presto. Problem solved! Checked the folder in which these files where located and saw that new versions had been created. URLs previously resulting in the error were again reachable.

BTW. For tech-challenged users such as my self the file path I used was: C:\Users\<my name>\AppData\Roaming\Mozilla\Firefox\Profiles\3ty54pzl.default-1465421084087