There is a known issue where the data_engine will not be able to establish a connection to a MS SQL Database despite the fact that the same username can successfully log in through SQL Management Studio, or a System DSN test, which is caused by an exclamation point (!) in the password of the SQL user that is configured in data_engine.
Some special characters in the UIM database password are not handled correctly preventing a connection to a MS SQL Server database.
UIM Server: Any version MS SQL Server: Any version
The resolution is to change the password to one that does not contain an exclamation point. Most other special characters should be fine.
Other special characters to avoid in UIM database passwords: