Adobe keeps asking to make Acrobat DC default PDF application

Hi,

I have a strange issue where I have set the iAppDoNotTakePDFOwnershipAtLaunch registry key for all users on an RDS farm.

For existing users the key is honored by acrobat reader DC, and they do not get asked the question to make Acrobat Reader DC the default PDF Application.

For new users however the key is set correctly but seems to be ignored.

When I start Acrobat reader it asks to be default.

When I choose "Do not show this message again" when starting then the option "Tell me if Adobe Acrobat is not my default PDF application" checkbox is unchecked in Preferences general.

When I close Acrobat and start Acrobat Reader DC again the checkbox "Tell me if Adobe Acrobat is not my default PDF application" is checked again and I get the question to make Acrobat Reader DC default once again.

Is there another factor besides the  iAppDoNotTakePDFOwnershipAtLaunch that is causing some users to get the question to make Acrobat Reader DC each time, and for others it doesn't (even though acrobat is not the default PDF reader for them either.) ?