How to set up a router for access via ddns?

Question

System administration

Good day. There is the following scheme:
Internet router1-router2-remote access server.
Access to the Remote Access Server is via rdp via ddns. Settings of Router1, Server did not change. Router2 spontaneously reset all settings on reboot. Having driven back port forwarding, ddns, dnz settings on the server, I still cannot log in to the Remote Access Server via ddns. Please tell me in which direction to move? There are suspicions that you need to somehow pick the settings for mac-addresses and wan ip.

Answer 1

In general, I do not know how it worked, but it worked!
In the settings of Router2, I simply entered the same mac-address to which the provider allocated an IP address and it all worked.

Answer 2

It is not clear what ddns settings can be on router 2. They should be on the first router.
Describe the network diagram more precisely.
Which router receives a white address from the provider?
Why is there a second router at all, and is there nat on the second router.
Did remote access work before?