Hello there,
This issue occurs because you try to start an application that relies on the Explorer.exe file. By design, the TS RemoteApp session implements limited functionality. For example, the TS RemoteApp session does not process the following items:
The Run registry entry
The RunOnce registry entry
The startup applications
Since RDP8.1, there is new function named dynamic resolution, if possible, try to disable this function via registry entry and check the result -> RemoteApp window is too large or too small when you use RDP to run a RemoteApp application in Windows Server 2012 R2:
Simialr discussion here https://social.technet.microsoft.com/Forums/en-US/49fe6a9d-96f5-4ef8-9194-e24a12db3a71/remoteapp-not-visible-when-launched?forum=winserverTS
Hope this resolves your Query !!
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