I can't connect to an instance of SSMS from other servers SSMS
Start by making sure that your Firewall isn't blocking incoming connections to port 1433 (if this is a default instance installation). Check both the Windows Firewall and also the settings on your network firewall ( if you have one configured ).

Also make sure that remote connections are enabled to the SQL server (in SSMS, right click the instance -> Properties -> Connections -> Allow Remote Connections to this server)