Site to Site VPN using IPSEC

I try to create a site to site VPN using IPsec, but I received this error from pep link

IPsec: Refused Main Mode connection request from

are there any ways to troubleshoot it?

hi, its interesting. your problem solved ? is there any configuration we can see overall network ?

You need to make sure your IKE setting match on both side:

Same key
Correct local and remote addresses
Same encryption settings.

Confirm that there is no firewall in place which will prevent the connection etc.