One of the drawbacks of running the thing through FTP instead of at the shell prompt is that you don't see any of the text output from any of the commands.

All FTP is telling us is that the program returned an error. The shell prompt might have been filled with tons of diagnostic text, but we didn't get to see any of it.

So at this point it would be best for you to run fidsift.sh from the shell prompt (change to its directory and type ./fidsift.sh) and see if it gives any sort of output or reason for a problem.