Creating a case seems to work but the case does not appear in the case list. 

adgbusinessservices log contains "case creation failed" and include the phrase "Failed to create AppDomain." 

An example of the error:

"Case creation failed.";"Error creating case: CaseId : 0, CaseName : TEST PROJECT 2016"; UserName : XXXX/XXXX; Error Number: 55d8270a-d0ab-4ca4-9914-0e23c2fc2666
System.Exception: Case creation failed. ---> ADG.Database.DAL.DALException: System.Data.SqlClient.SqlException (0x80131904): Failed to create AppDomain "Case_ADG57_2373.dbo[runtime].12".



Reboot all servers. Especially the SQL server. 



This is usually caused by an update, typically for .NET, being pushed to a server (usually the SQL server), leaving the server in a pending for reboot state. SQL logs will indicate this.