The first thing I would try is:
Pull up your App Manager and swipe the game away. Swipe away all other open apps as well, just in case.
Turn off your device.
Turn off your modem, router, and all other internet hardware. Wait 15 seconds. Turn your internet hardware back on, starting with the modem, and wait for them to boot up.
Turn on your device. Start the game. Try to log in making sure you spell your email address correctly.
If that doesn't fix it...
Repeat the above, but before you turn off your device un-install the app. After you turn the device back on re-install the app, start it, then DO NOT touch the screen other than to enter your age and agree to the license until ALL the updates have finished installing.
If THAT doesn't fix it...
You shoud contact Customer Support. When setting up the case select "Technical support" as your Topic and select your Platform, then scroll down to the bottom of the page and hit Contact Us..
If the game is saying that the credentials are invalid, you should head over to EA.com and reset your password, to do so just follow these steps:
As long as you do this you should be able to log back in without loosing any progress.
I've tried all the above and still get the Invalid Email prompt and when I want to get a new password, I get no email anywhere. I've spent quite a bit of cash on some of the buildings, jobs and characters and just want to get back to playing my game.
I had to use an old email address just to compose these messages.
If you have followed the instructions I provided but have not received an email, there could be a technical fault. Please follow these new instructions:
Do not contact them from your ios device. Use a pc if possible and pick live chat. The link that was provided was for the Simpsons Tapped Out, instead go to https://help.ea.com/en/contact-us/new/ . Now click on Origin as your product. Then for topic, select Manage My Account. Then type in "can't log in" as your issue and click next. Select the live chat option or request a call back.
You can also contact EA using Skype. This can work on an ios device. Download Skype. Then use voice over IP service to UK Skype chat: +44 203 0141818 You can also do the same from a pc.
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