Does the SQL Server instance has a name, if so you have to specify it:
data source = <ip>\<instance>
Check this site, it has some examples:
https://www.connectionstrings.com/sql-server/
Also check if the servers can communicate with each other. (firewall, etc.)
data source = <ip>\<instance>
Check this site, it has some examples:
https://www.connectionstrings.com/sql-server/
Also check if the servers can communicate with each other. (firewall, etc.)