When you restrict a forum to admins/mods, you must update your moderators profiles to grant them access because that permission only allows the mods of the restricted forum to go in.
Donate to UBBDev today to help aid in Operational, Server and Script Maintenance, and Development costs.
Please also see our parent organization VNC Web Services if you're in the need of a new UBB.threads Install or Upgrade, Site/Server Migrations, or Security and Coding Services.