I had a server running on windows 10 through AT&T, but I have since moved and switched to TDS. I have completely removed my agent and tunnel, re-downloaded the agent and set it up from the beginning. I used my servers local IP address (and even put the IP on a port forward for 25565 in and out though playit doesn’t need a port forward).
No matter what I do, the web portal shows that there is no handshake between my network and playit servers. My local network has a GPON/Modem that has Routing set to bridge, and an AP/Router combo. It seems like a network issue for sure, but I am unsure what I would even ask my ISP to help fix to remove this issue.
As most network people will chime in right off the bat, it’s probably your DNS. 
Do you know what DNS provider you’re using? Have you tried different DNS serivice?google (8.8.8.8), cloudflare (1.1.1.1), quad9 (9.9.9.9).
I’ve had different modems try to inject their own DNS, which was supper annoying. You may see if swapping the DNS service on the computer you’re using it on may help.
I had my router set to OpenDNS, but I have changed it to 9.9.9.9 with secondary 1.1.1.2
On my server, I did a DNS flush and set it to the DNS listed above.
I am still not able to get a connection to the server over PlayIt.gg IP. I can play on the server through its local IP, but that is it.