During a tidy up of Active Directory I moved some security groups used by VMware AppVols to a new OU. The side effect of doing this is that no AppStacks were being assigned on new logins to Horizon View desktops, oops!
The easiest way to fix this is to remove the assignment from the AppStack
Rename the security group in Active Directory
And the re-assign the security group to the AppStack
This fixed the problem for me. Hopefully it will help you as well