Did you login to Facebook or Game Center from within SimCity BuildIt?
If so, then your city is safely attached.
1) Go into your iPads "settings > SimCity", and write down your SimCity ID, just in case you need to send it to support later.
2) delete the game and reinstall it
3) painfully get through the tutorial
4) you'll then be able to access the settings and login to either facebook or game center. It will ask if you would like to overwrite the new city with your old one.
That might not fix your problem. Maybe there's a connectivity problem to your SimCity server from your area. I would also try rebooting your device, and possibly your router too.
