@Alexander
I will try registering my second email. It's a proton as well. See what I get. I haven't heard back from Panzer but the rolls went through. Previously it would throw a error if your opponent wasn't registered when you rolled the battle.
@trout I would go here and register and see what happens
https://dice.triplea-game.org/
Edit
I just registered my protonmail and didn't get any error message. So Idk what's up. I guess we'll just have to see if it works for you guys.
I might try a test game with my gmx mail and see if it works
Edit 2
Looks as if the Dice Registration error has been fixed. I tried to reregister and it said I was already registered. So I suspect you and Panzer are too. You can try it and see what it says.