After I upgraded KSC to the v11, in some of my pcs, avp.exe is missing and I have to manually remove and reinstall KES. I think this is happening during the KES upgrade from 11.0.0.6499 to 11.0.1.90.
The problem also occurred when I tried to upgrade KES from 11.0.1.90 to 11.1.0.15919.