Maps VTT Issue with Wifi and LAN connection

Good Morning,

Up until very recently I have had Xfinity for my ISP. Modem and Router were my own that I purchase and maintained myself. Everything has ran just fine for us using DnDBeyond Maps VTT;  our DM using his Samsung tablet on Wifi to launch and run the DM side of things while I have a TV with the VTT on top of a table. Historically, I had been using my laptop on Wifi, but 3 months back I had also picked up Quantum Fiber and shortly after switched to an old Tower PC on a LAN cable for running the VTT, to mitigate bringing down my laptop every time. For those 3 months everyone still had been running on the Xfinity Wifi and the VTT was on LAN also through my ASUS router on Xfinity. I have since discontinued my Xfinity service 2 weeks ago, and this past Sunday when we were running solely on the Quantum Fiber our DM booted up as normal, connect to the Fiber Wifi and launched the game, I spun out the TV VTT on the Tower and it would sees the internet just fine and DNDBeyond, but gave me an error when attempting to connect to the current session.

Error Message:

"It seems a wild Disconnection has thrown us off our path! Roll for a refresh to restore our Connection Saving Throw and rejoin the quest.
If the disconnection spell continues to haunt you, please seek the wisdom of the supporting mages support." *the link goes to the VTT FAQ*

Everyone else can spin up the Maps VTT session on their phone across the Wifi just fine, but the PC on LAN is the only one that has issues with connecting to Maps VTT session. Everything else is fine and has been fine until the recent switch over to everything being on the Fiber network now. I grabbed my laptop for that session and that, via Wifi, can see and connect to the Maps VTT session just fine. To reiterate, the LAN PC(being Windows 7 and using Chrome browser) accesses the internet just fine and only has issue connecting to VTT session when we switched it to the Fiber ONT/Pod.

I have spoken with Quantum Fiber 1st and 2nd level support and they were not very helpful with figuring out a resolution. They did do a firmware update for the Fiber equipment, but that did not help. I have ran a few test and moving the LAN from the Fiber pod to the actual ONT port, putting LAN connections to the DMZ... all no dice. 

I am looking for ideas on what might be causing this non-connection on the PC via a LAN connection that DOES see the internet just fine, but has issues connecting to a Maps VTT Session. Is there certain port(s) that need to be opened for the VTT in the Fiber ONT? 

The standard Quantum App for accessing 'control' for your network for the Wifi 7 360 , is a joke. I have gained access to the ONT login information and can gain access to some more opens that way, but is still very limiting compared to the full access I had with my personal owned equipment I used for Xfinity(Cable Modem and Asus Router). I also, tried hooking up the Asus Router as an Access Point only and tried hooking both the LAN to that and connecting my laptop to that router's wifi to see if that would make a difference and it did not. Also tried laptop on Fiber Wifi and LAN on ASUS router, nope. I switched so LAN was on Fiber and Laptop on Asus router access point wifi, also nope.

My going theory is that the Fiber's ONT might need a port opened for the LAN side to properly use the Maps VTT... but I do not know what that is. I am open to ideas and suggestions. Going back to Xfinity is not a solution, so if we could skip those ideas and/or comments that would be great. 

Thanks!

As your laptop works on the same network over wifi but the LAN PC doesnt, I do not think this is a router port-forwarding issue. If it were, neither device would be able to join the VTT session. The bigger thing that stands out is that the LAN PC is still running Windows 7. D&D Beyond Maps relies on newer browser and WebRTC/WebSocket features, and Windows 7 is no longer supported by Chrome. Its possible something changed on the VTT side recently that older Windows 7 networking components can't handle anymore. test by booting that PC with a newer OS (or another PC on the same Ethernet cable) before spending more time on the ONT. If another Windows 10/11 machine works over the same LAN connection, you have found the culprit. Also check whether Chrome on that PC shows any WebSocket or WebRTC errors in Developer Tools (F12 -> Console/Network) when trying to join the session. That can usually point to what's actually failing.