First off this is not a default program setting issue. The defaults for .pdf and .pdfxml on multiple machines are Acrobat Reader DC. However when I double click on a pdf from any of the multiple workstations I get a cloud login. When I supply the login user/pass the pdf opens in Pro. Even if I right click open with Acrobat Reader DC there is a login and it goes to Pro.
The only way I can get a pdf to open is to open Acrobat Reader DC and then File>>Open the pdf.
This will happen if Acrobat Pro is already running, even invisibly. So check in Task Manager for a running copy. But also check your Acrobat/Reader preferences, where the default app is set (as well as in Windows).