My first guess is that this is a file permission issue on his local machine. The Dynatrace client wants to write into USERS_HOME/.dynatrace/. It's possible the client was installed using Admin, but now your user is trying to run the client with user level permissions which are too restrictive on his local machine. The Dynatrace Client log might help, but there might not be such a file if he has a file permission issue.
Can you have him RunAsAdministrator and see if that helps?