Hello Jaockim,

The error might occur if

a.) Remote connections are not enabled on SQL Server.

b.) The necessary protocols for are not enabled either SQL Server computer or the SQL Server client computer.

If you can login to the Computer running SQL Server,

Login to the instance locally and open properties of the instance

-> Go to Connections and see if Remote connections are allowed

--> Open SQL Server Configuration Manager and see if necessary protocols such as 'Named Pipe, Shared Memory. TCP/IP' are enabled. (You might want to refer to another computer's settings which, you are able to connect remotely.)

Let me know if it helps.

Regards..