The app won't open. I can't log in.

A lack of device memory/storage or your internet environment could be causing the problem.
Please try the procedures below:

<iOS>
-Close other apps/browser tabs.
-Restart device instead of putting it in sleep mode.
-Sign out of Game Center and sign back in.
-Free up storage space:
Check the amount of available storage on your device and delete unused apps if necessary.
-Re-install app after configuring your data transfer settings
-Change your internet environment:
Try restarting your router and/or clearing the cache.
Try switching between mobile data and Wi-Fi to see if the problem persists.

<Android>
-Close other apps/browser tabs.
-Restart device instead of putting it in sleep mode.
-Sign out of Google Play and sign back in.
-Free up storage space:
Check the amount of available storage on your device and delete unused apps if necessary.
-Re-install app after configuring your data transfer settings
-Change your internet environment:
Try restarting your router and/or clearing the cache.
Try switching between mobile data and Wi-Fi to see if the problem persists.