Thanks for taking my question Koen. I also read about this during initial research of problem, but ....

(1) I installed sql server on this machine myself (I am learning) and accepted only default settings ie. didn't set the port name and IP address.

(2) The data connection wizard in Excel does not have any fields where one can provide an IP and port number. It asks only for server name and logon credentials (windows authentication or name/password). I provide server name and use windows authentication.

Can you see other possibilities?