I elevated an application, but drag and drop between the elevated and other non-elevated applications isn't working anymore. What can I try?

When Netwrix Endpoint Policy Manager (formerly PolicyPak) elevates a process it also changes its Integrity level.

NOTE: To learn more about this topic please see the Microsoft article on What is the Windows Integrity Mechanism?

As such, a newly elevated process may not be able to communicate with a normally running process.

That being said, you can reduce the Integrity level of the process which is running elevated. To do it, instead of selecting Run with elevated privileges, choose instead Run with customized token.

This enables you to change the Integrity level. You'll want to try Medium-High first, then fall back to Medium or Low, stopping at the first one which works.