Client just went live on a new RDS server (2016), they run from a published app for Sage 100, they are using paperless office for journals and registers. Users are getting the message below:

Adobe Reader DC is installed. This does not happen to me (domain admin) when logged into the server nor when using the RDS App. IT also created a test user with the same rights as ordinary users (at least we think it's the same) and the error does not display.The pdf's are getting created in paperless, and the program continues on and allows the users to update (without seeing the register/journal).
IT is at a complete loss as to what to do. I am thinking there is an association for the '.pdf' extension missing for all the users somewhere?
Any ideas? TIA.
------------------------------
Greg Stiles
S & W Microsystems
Torrance CA
310.787.1010
------------------------------