Do you have a Sonos device wired directly to the root Velop device?

No. All sonos devices (play:5, arc, amp, port) are all connected via wifi. 

That could be an issue. Sonos recommends a wired setup in a mesh network. 

There is a lot of inter communication in between Sonos speakers, if they’re not on the same subnet as many mesh systems do, they can have difficulties. I’d suggest temporarily wiring at least one speaker to the root hub, and see if they all show up again. If you’re unable to keep a speaker wired due to location issues, a BOOST is the solution I use. None of my speakers are close enough to my root device, so the BOOST takes that place, and puts all my Sonos on the single SonosNet network. If you do end up going this route, I would then recommend you remove your WiFi data from the controller, so the speakers aren’t constantly trying to flip between your own WiFi and the Sonos network. 

That makes sense. None of my speakers are near the root device but would wiring my arc into one of my wireless nodes maybe work? My arc and one of my wireless nodes are both sitting in my entertainment center so could be an easy fix. 

Much understanding is it needs to be the root, and not one of the extension nodes. Try temporarily moving and wiring a speaker close enough to the router/root device. If that fixes the issue, consider purchasing a BOOST. 

Thanks Bruce. That makes sense that it would need to connect to the root. 
I appreciate your input. I’ve got a couple things to try now. :)