Obviously, the key/value that filemaker uses to generate that function's results have changed with iOS10.
Have you updated to filemaker go 15.0.2?
FileMaker Go and iOS 10 compatibility | FileMaker
If you have, and completely exited and restarted the iPad and filemaker go, then it may be a bug, which you can report here:
Yes FileMaker Go 15.0.2
Yes I restarted