Question:

After we migrated our domain controllers from Server 2008 to Server 2012, the Deskpro Active Directory app stopped working. 

Using the Test Settings button returned 'An unexpected failure occurred 0x51 (Can't contact LDAP server): ldap://<domain controller name>:636'.

What's happening?

Answer:

This happens when your Active Directory configuration requires you to search the Global Catalog.

In the Deskpro app Server settings, change the port to 3268.