If you cannot open any app, see any thumbnail image or extension then that signals that something is wrong with the service account's access to the share used to host Qlik Sense (QMC > Service Cluster). That could obviously be at the Share or NT levels since Windows evaluates both permission sets.
Another signal that this is a problem is if there are .log files in C:\ProgramData\Qlik\Sense\Log\Repository\Trace. These .log files should archive to Service Cluster > Archived Log path on initialization of Qlik Sense.
As for logs, check the System_Repository logs in C:\ProgramData\Qlik\Sense\Log\Repository\Trace it likely is complaining about something.
