Question for Best Practice/Wireguard

[PotatoCarl]

Hi

I have successfully setup one Wireguard VPN. It works inside out network and outside. So Yay!
However, I copied this VPN to a second one, differences are: Different port, different IP range.
I cannot get this to work, i.e. my client does not show "handshake".

Few things:
- We have two WAN, so both Wireguard clients have 2 peers
- The WAN is coming via a fritz box and exposed host to the OPNSense port
- The different IP ranges are necessary as in our experience from time to time e.g. Hotels use the same internal IP range as we do, so no routing is possible. Therefore we have multiple VPN instances to make sure "one of them works"

I know, I know "I copied everything but..." usually means "but forgot something". I have checked mutiple times all settings (gateways, interfaces, rules, NAT, shaping, Wireguard) and cannot find a difference.
Basically I am asking where to look protocol wise to do debugging. Or any other tip if this is fundamentally wrong what I was thinking.