Hey guys I have been working with support and I have been able to get Adobe Acrobat DC 2015 and 2020 to stay licensed during the end users session.
Here is the two methods that worked for me.
1. Using the App Volumes Migration Fling migrate the working 2.X Appstack to 4.X package. Support suggested this and it worked. This did not require DEM logon task to work. App Volumes Migration Utility | VMware Flings
or
2. DEM Logon-Task which adds the license after logging in.
Logon Task
Command line: adobe_prtk.exe --tool=VolumeSerialize --stream
Timeout: 10
DEM privileged elevation for Adobe_PRTK.exe Tool
Captured Adobe Acrobat completely without license.
I tested both methods and seems to be working. Let me know if this works for you.