are you opening up a hosted file, or are you moving the .fmp12 file to the device itself to use it? Please take some screenshots of the error so we can think about it further.
Also, in terms of the iPod, Filemaker Go 12 is "compatible", but the apple store says that it's optimized for the iPhone.
Is your iPod up to date with the latest version of iOS and FM Go?
I'll post the info when I get the error again. Cheers Joh