No TXs processed

Sounds like it might be a port issue. Your nodes will stay in sync as they can make outbound connections, but they cannot process inbound transactions if the relay port(s) are closed to inbound traffic.

Check your relays using this tool to ensure your relay ports are open (make sure the nodes are indeed running):

Can you confirm whether or not the relay ports are open to inbound connections?

Here is a guide to addressing port firewall rules: