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!)
