Please try logging in and out using the Game Center app (reboot before logging back in). Restart Bard’s Tale and see if you get a "Welcome back" Game Center message. If so, then go to the Game Center page from the main menu and select "Synchronize Achievements".
Please also make sure you have the latest versions of both iOS and The Bard's Tale, as well as OS X if you have a Mac desktop computer or MacBook, as achievements are shared across platforms.