Swarm Coordinator not working

my swarm was working moderately well on 4.13 - but after updating to 4.15.3 the coordinator no longer sees the computers on the network.

I noticed the IP changed, so I updated that on both computers, but still no luck.
I noticed the old shortcut was pointing to the swarm version from 4.13, so I updated the shortcut, does that even matter?

Any help would be greatly appreciated.

Swarm has always been extremely frustrating. gr.