It isn’t impossible, if you browse the forums you will see several instances, it is/was a bug (which didn’t effect everyone) most commonly triggered by system restore, but not exclusively. But that bug should be resolved in the latest avast version, but first you have to get to the latest release.
For those with those problem a clean reinstall to the latest avast free version would also resolve it.
As mentioned, more commonly it ended up being converted to an expired Pro version.