I have two servers

1… Server1 – connected in a company network with fix IP behind firewall
2… Server2 – part of the company network, but connecting using the VPN over Internet – dynamic IP (login using the network account for remote access)

When I try to register SQL Server1 on SQL Server2 it works fine… but while trying to register SQL Server2 on SQL server1 throws the error ‘SQL server does not exist or access denied. ConnectionOpen(Connect())’

I need to connect these servers for synchronization over Internet via VPN. Do I have to check any settings in firewall or VPN or SQL ? if yes what and how ?

Can somebody pls. guide me to resolve the issue… many thanks in advance…