Best way to replicate certificates between sites (no HA)

[With Wings]

I've been able to export the certificates using the links in the web interface, and then copy pasting them into the import fields on the other sites firewalls.

The issue I'm having is trust for the CA Cert. The Server Certificate for one of the VPNs is showing self signed, and the CA Cert for that VPN shows having signed the Users certificate for that VPN, but not the Servers.

To be clear I'm using a different CA, Server, and User certs for all VPNs. In order to segment the network.