Syncup Kids App

Any idea why I can't log into the Sync Up Kids app on my iPhone 11? According to the App Store it should work (new enough iOS version) but when I try logging in it says that the app is experiencing problems. However, I am able to log into the SyncUP app on my iPad so it's has to have something to do with it not jiving with my phone. I have uninstalled/reinstalled the app along with turning my phone off & back on.