Unable to join game hosted through Zero Tier, but was able to before.

[Oakrose905]

So me and a friend have been playing the last few days together through Zero Tier, with them hosting. Its been working fine for the last few days and even earlier today, but now after a few hours of a break and them starting the game back up, I can no longer join them. It reads as having no connection, however, we checked our Zero Tier connection and it was still ongoing, we have tried restarting ZT, the game itself, and even our computers and it still won't let me connect. Any ideas on what is wrong, and how to fix it?
Below is what it keeps saying when it fail to connect.