I'm trying to record my buddy's guitar by plugging it into one the H4n's hi-z inputs. There are no levels coming through. Is there something I need to change in my menu in order to get the audio to come through?
Check your guitar cable. You should be getting too much signal, if anything, rather than none. Make sure the input works on the H4N (plug a microphone in). Check the input signal level adjustment (I believe the input on the H4N can be adjusted within a broad range; you may have it set too low).
GJ
PS-- At least, that is a common problem that H4N users have reported when trying to record guitars directly.
Does the guitar and guitar cable 'work' normally with other devices? an amp for instance. If "Yes", this suggests the guitar and cable are OK and the problem is with the recorder. Basic troubleshooting
Another possible cause: Some acoustic guitars with internal pickups have 'active' electronics and need a battery.