"Forget" about Avast for a moment
.
1_ Reboot;
2_ Open Windows Security Center;
3_ In Windows Security Center,
Deactivate the Windows monitoring of Avast (or any antivirus that Windows is monitoring) (so Windows WILL certainly tell you that the system is UNsecured);
4_ Reboot;
5_ Open Windows Security Center;
6_ In Windows Security Center,
REactivate the Windows monitoring of Avast;
7_ Reboot;
8_ Check for updates (both for Windows and for Avast);
9_ Reboot.
10_ Come back with (positive/negative) feedback/results.