SSMS Cannot Connect to Newly Installed Instance (2017)

SQl Server 2017 Standard
Installed 2 days ago.
Was able to connect to the instance via Management studio v18.1

Yesterday server was rebooted
Now when I attempt to connect to the instance I get:
"Cannot connect to MyServer.

Yes the SQL Service is started.
Does anyone have any ideas?

By specifying the port number, I can connect via SSMS

ServerName, 99999 works
But why, out of hundreds of instances, do I have to specify the port for this one?