External addresses from the same subnet from the same provider do not see each other?

Question

Network administration

2 external addresses from the same provider, the first address on one router, the second address on another remote router. Routers do not see each other, so I can not configure vpn. Addresses in the same subnet, with the same gateway, mask, dns. There is access to the Internet, routers support up to dozens of vpn, there are configured vpn with other external devices from other providers. Disabling / enabling the firewall, setting the policy of incoming / outgoing traffic does not affect the problem. Feeling as if these two addresses are in different vlans on the provider's side, if possible. Other providers see them and they see other providers, but they do not see each other. I hope the point is clear.

Answer 1

Before making such global conclusions - make a simple traceroute
being at the first address
traceroute the second address
or
tracert the second address if you have Windows
Solution:
Write (or call) to those. provider support.

Answer 2

The problem was on the ISP's side. They don’t say what exactly, but they removed the checkmark. Well well.