Why is the AD400 unlocked after I tested it with my SUS/HHD.

Look to see if the  "Fail Safe?UNLOCK" on communication failure is set and you have lost communication.
The "Unlock on READ" from diagnostics will clear with the next AD400 heartbeat, automatically. It will also clear with successful communication to a working access control panel. 

 If the AD-400/AD-401 is LINKED to a PIM400-TD2 and all credentials including invalid cards are granted access, the PIM400-TD2 is not communicating with the Access Control Panel, and the lock is stuck in an “Unlock on Read diagnostics” mode.

To cancel “Unlock on Read” from diagnostics, use the HHD at the PIM400-TD2 to uncheck the diagnostics menu “Unlock on Read” box.

Or force a strike input to the PIM400-TD2. Short J8-1 and J8-2 (Door 1), Short J7-1 and J7-2 (Door 2) on the PIM400-TD2

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