I have a server running SQL Server 2022 with a couple of instances. There is the need to grant access to an external supplier working with us on a project. The idea is: the supplier connects to our sql server on a specific database they need to access. We have created a configuration on a proxy server running nginx that allows the connection to the local sql server. However, I cannot reach the database when testing from outside.

Is there any configuration I need to do on the SQL server to allow this hebavior?

This is what I tried so far:
Created the rule in the proxy server and attempted to access from external network to see if it could work.
It did not work but I can see the proxy is being accessed and I can access the iis default page on the database server.
However, I cannot access the database.

Thanks in advance!