Recently in one of our application while trying to configure  reporting services configuration we were getting the below error while trying to connect to a SQL database.

Checked the remote server connections for the database and it was enabled

Went into the component services and checked the local DTC connection

Network DTC access was disabled and hence the issue.

Enabled them and after MS DTC service restart checked UDL connection for the affected database on that instance.

In addition to the above we can also check the execution account permission on the SQL database server.

This can also happen if the SQL service state is not running.

Make sure SQL Server service status is Running.
Also make sure the TCP/IP communication is enabled on the SQL server configuration manager on the instance where the problematic DB exists

By default SQL Server runs on port 1433, if the default port is changed then these new ports should be added in the firewall exceptions.

You can also check the connectivity to the SQL Server by the below commands

netstat -ano| findstr 1433

You should get a successful  TCP listening establishment on the SQL server IP address and on port 1433 .

Hope this helps

Thanks & Regards 

Sathish Veerapandian 

MVP – Office Servers & Services