I think I now have found a workaround to my issue:
I saw that AMT is detecting the product language as en_GB instead of en_US so I played with the ACW11 settings.
I recreated the MSI/MST using ACW11 and changed the following options:
Serial Number -> “Grant Offline Exception”
Installation options\Set the language to the OS language, but let the user… -> deactivated
Maybe I'm just masking the root cause of the error this way but at least it works. After several starts of Adobe Acrobat, the product now properly goes from serialized to activated state.
At that point I also get a swid.tag file in “C:\ProgramData\regid.1986-12.com.adobe\”
amt3.log in user's temp then has the following entries:
…
...
AMT: AMT: Product License Validated.
…...
AMT: Application licensing status has changed to activated.
…...
AMT: Prevalidate indicates license is good and no UI required....
...
regards,
Nik