RHEL users get error "could not open session" when trying to su

Issue

• I have several RHEL boxes that are posting the following error when the users try to su or sudo to another UID.

• I can ssh into the box without any problem as root or as my regular user, but when I try to su or sudo to another UID we get the error.

[root]# su - testuser
could not open session

There is nothing in the logs that indicates why this is happening. I've rebooted the box and performed an fsck on the partitions to verify that they are all good.