If you have upgraded your device to Jelly Bean, you may have run across a PinCity bug not previously present. Under some circumstances, the map doesn’t show, making it (sadly) impossible to play. The problem only arises when going from the portrait (upright) game menu into a landscape map (such as the World or US maps), or from the landscape game menu into a portrait map. I’m investigating the exact cause for this; in the meantime, a workaround is available: if the map is missing, just back up into the menu, rotate the device (you’ll need to have auto-rotation turned on for this), and try again.
I’m sorry for any inconvenience, and hoping to have the issue fixed soon.
Edit, Feb 26: The issue has now been fixed. The fix is included in version 1.16 which should be available at Google Play very shortly.