Right-click TCP/IP and choose Properties (ensure it’s set to enabled)
Click into the “IP Addresses” tab
There will be a section for each IP address that the machine has – including for the “localhost” address and also for IPv6 addresses
Go through and “Enable” all the IP addresses that are needed.
If you don’t know the correct local IP address, a simple “ping <servername>” will determine which IP address your current machine resolves to when referring to it by it’s hostname
If unsure, consult a SQL or network professional to assist before making any changes.
Click OK
Restart the SQL server via services or the “SQL server services” item in the configuration manager.