Issuer of server certificate expired

[easm]

Hello, Just recently it seems that nearly every web site I have a log in for and put my details in to access it I get a pop up from avast saying ie.
"avast blocked access to (https whatever) because one of  the issuers of the server certificate has expired".
I have mailed my utility company about this who have yet to reply to me but I think it's an avast problem as it flags up this message all the time with various sites.
As I am hopeless in getting these sort of problems sorted I would appreciate it if someone can shine a light on this most annoying, frustrating problem for me.
Any help would be most appreciated thank you.

[Asyn]

Hi, probably related to: https://scotthelme.co.uk/lets-encrypt-old-root-expiration/

[patrick8888]

exact same kind of stupid issue has popped up here, maybe 60-90 days back first appeared, probably since some kind of "upgrade/update" of Avast itself, has denied me access to sites like Quora and Unherd ever since...3aw.com.au  radio station site too. 

see screencap attach . See bottom right cnr of it in particular for Avast popup.

So, they have an exceptions list, right, you can type in site/page names you do not want antivirus to interfere with/block ?
Great...maybe I can eliminate the site blockages one by one..

So I type in Quora and Unherd for starters, into the exceptions box. ...

now you get another retarded message telling you that the certificate cannot be verified or site accessed because...your clock is incorrectly set (ahead).
No..For my time zone..my clock is set perfectly.
Tried 10-min or session temp disabling of Avast . Again with the stupid 'your clock is incorrect" message.

so I figured that this was either something that cannot be fixed because I have an older operating system..or something where the fix is something so abstract that only makes sense or steps which can be followed to a techie.

Either way, so angry, close to uninstalling fkg Avast and having done with it.