My neighbor gave me this fix for my desktop with windows 10;
"I had the same annoying issue. It is easy to fix. Go to control panel, programs and features, click on Avast, then click uninstall, then click repair. It only takes a minute or so and fixes the issue."
This worked for both of my computers just last night, on one of the computers I had to run the repair twice.
Edit to add; I didn't uninstall Avast, just clicked uninstall, then the option to repair popped up and I selected repair.
Leonard.