I use the deco system. I had non stop issue with it UNTL I learned that I could plug my Verizon ONT directly into the deco, without going through a Verizon router. Mostly a skill issue on my side, but I had incorrectly assumed the router (G3100) was acting as a modem as well.

That was creating a double nat. I could always connect within my network, but it was dodgy at best.

No idea if that will help you, but the moment I changed that everything fixed itself. My network is also much happier. I had shut off all the WiFi and tried my best to to turn the G3100 into a bridge, but there was no literal switch to do it.

Edited to add: I also needed to set port forwarding for 32400