This has been a problem lately. I've had to deal with it as well.
A. Make sure your password is less than 16 characters long and does not have any special characters - just letters and numbers.
B. This worked for me:
- Open the App Manager by double tapping the Home Button (Apple) or tapping the rectangle (Android).
- Swipe away all open apps (people call this force closing, but that is not correct, this is just closing the apps)
- Turn off your device. OFF. Do not restart.
- If you're using home internet to connect, turn off your home internet devices.
- Wait 1 minute.
- Turn your home internet devices back on (if applicable) and wait for them to connect.
- Turn on your device.
- Try playing.
C. If the above doesn't work:
- Open the App Manager by double tapping the Home Button (Apple) or tapping the rectangle (Android).
- Swipe away all open apps.
- Uninstall the game.
- Turn off your device. OFF. Do not restart.
- If you're using home internet to connect, turn off your home internet devices.
- Wait 1 minute.
- Turn your home internet devices back on (if applicable) and wait for them to connect.
- Turn on your device.
- Install the game.
- Start the game but DO NOT TRY TO PLAY
- Enter your age and agree to the license.
- DO NOT LOG IN AT THIS POINT. Wait for ALL the files to download. When ALL the files have downloaded THEN log in.
See if that works.