Can't connect anymore after first launch – "API server unreachable (GetRules endpoint)"

I downloaded Sodoff today and was able to play for a little while without any issues.

After closing the game, I haven't been able to get back in. Most of the time it gets stuck on the loading screen before the main menu. If it does reach the login screen, I get this error:

"API server unreachable. Check your connection (GetRules endpoint)."

I've already tried:

- Restarting the game

- Restarting my phone

- Switching between Wi-Fi and mobile data

- Uninstalling the game and reinstalling it

Has anyone else experienced this? Is it a server issue, or is there another fix I should try?

( I use Android)