I believe the reason why people are having issues with this game and some others is due to Apple preventing sideloaded apps from connecting to Game Centre. I think it's an update that came with version 14, so 13 and below, you can still use sideloaded apps without issue. I think the only way for people stuck with the latest IOS update to use modded applications is to wait until the IOSGods app gets a new profile and we can download straight from the application, but I'm not sure whether Apple has covered this grey area or not.
Anyhow, we can only wait and see. It would be nice to get more consistent or informative updates from the team, but beggars can't be choosers.