Hi,
Location of fop2.cfg file depends if it was installed from tarball or from .rpm. Not sure what are you quoting, but you do have spy_options over there. You can remove the "b" from it and try again.
Reinstalling fop2 won't make any good, you have to just fix the config on your system or your system per se. As I said before, fop2 launches/fires a command in asterisk that in turn fires the chanspy application to snoop on the call. Once the command is fired, fop2 does *nothing else*, asterisk takes control: your phone rings, when you answer the application starts. If sound comes garbled, low, non existant or whatever, it is asterisk/chanspy, not fop2.
You said that your phone rings and hear silence, try this: answer the phone and keep it hearing the silence, while you run this command:
asterisk -rx "core show channels concise"
Look at the output, find *your* channel, and see what is it running.. you can post it here, but be careful to not disclose potential private information. If you see that your device SIP/something has Chanspy running with parameters SIP/somethingelse and seems correct, but you still hear no sound. then it is not a fop2 problem that you have to fix, but your asterisk.
Best regards,