Unable to connect to SQL Server in Qlik Cloud desp… – Qlik Community

First you should check the data gateway section of the management console and make sure your gateway is connected. If it isn’t connected fix that first.

Next, connect to the gateway server over RDP and test if you can communicate with your database server from the gateway server. Try a simple ping first and if you can try telnet so you can check to make sure the sql server port is open between the two machines(1433 is the default) 

After that I would make sure the of the address of the SQL Server weather you are connecting to the default or a named instance of SQL, for example.

If you cannot do any of this then check with your Qlik Administrator and see if they can troubleshoot it.