Did Not Connect: Potential Security Issue

First, apologies if this is the wrong forum for this question. I have been a Firefox user for many years. Recently I installed the Avast Ultimate package, which includes Premium Security, AntiTrack, Cleanup, and SecureLine VPN. I also installed BreachGuard. Since that time I am getting the following when I try to connect to some pages, such as YouTube:

"Firefox detected a potential security threat and did not continue to accounts.youtube.com because this website requires a secure connection.

What can you do about it?

accounts.youtube.com has a security policy called HTTP Strict Transport Security (HSTS), which means that Firefox can only connect to it securely. You can’t add an exception to visit this site.

The issue is most likely with the website, and there is nothing you can do to resolve it."

Has anyone else encountered this problem? If I switch to Chrome or Opera, for example, YouTube access is normal.

I am using Firefox 100.0.2 (64-bit) on a 2020 MacBook Pro when this is happening.

Please advise and thank you in advance for your help.