SQL Server does not exist or access denied.

Hi folks and friends, I am posting here an image of an error message. I encountered this error message while using Microsoft Excel.
Microsoft Excel
[DBNETLIB][Connection Open (Connect()).]SQL Server does not exist or access denied.
OK
When I read the instruction on the error message, it tells me to check my connection to the server, as I am checking my network connection, there is nothing wrong with my connection.
I also checked my firewall, there is no restriction for such connection towards the server, that is why I am wondering what other reasons that led to this error.
Please help me find solution to my problem.
Thanks a lot for reading my post.
