If your user has limited permissions, there are no other solutions other than using the manual QLM method to activate, which has been reported to be working by several users.
If it's now in Trial, it means you must have changed the users you are running MSFS with, so activate it again using the QLM method with the current user.
I strongly suggest giving your user full permission instead, which will make everything ( even not related to GSX ) working more reliably.