Ended up figuring it out with SAS TS. Apparently the SSSD service on one of the nodes wasn't refreshing and any new users added to the Active Directory group wasn't being recognized on this node. In working with our Linux admin, once SSSD was stopped, cache cleared and restarted, it resolved the issue.
For reference, this was what was run to refresh the SSSD service...
service sssd stop ; rm -f /var/lib/sss/db/* /var/log/sssd/* ; service sssd start
Thanks,
John