(Fixed) Web and Email Shields not working on Big Sur

I upgraded to Big Sur, and now both my web shield nor email shield are reporting an error: “We’re sorry. Your mac didn’t load our extensions.” There are a lot of posts mentioning this problem, but I don’t see a clear place where the fix is described. Thanks in advance for a pointer to how to fix this. (Fixed by updating to latest Avast. I assumed that Avast was self-updating. It isn’t! Virus defs are, of course, but core software isn’t!)

Hello,
thanks for reporting the issue. Please check your email for further details.
Kind regards,
Ondrej Kolacek