I can’t say how many various problems I’ve had connecting to SQL Server. I’ve lost count at this point. This was the last one I had, which I’ve encountered a number of times and always successful to fix it.

Cannot connect to x.x.x.x.

Additional Information:
A network-related or instance-specific error occurred while establishing a connection to SQL Server….

Now usually when I encounter this error, I do something suggested here at Pinal Dave’s site. This time nothing mentioned there worked. What did work, was me explicitly selecting the Network protocol, and not leaving it as the :

Still wondering why I have to do this, as I’ve never had to explicitly select the protocol before, and nothing on the server has changed in years. Will continue to investigate.