Either nobody is sharing what you're looking for, or they're ofline at that time. Keep in mind people from all over the world use gnutella, some of them connect at different times to you. Also there's some people who only connect perhaps once/few times a week or month or weekends, etc.
Personally, I almost always use the Any Type general search as i find it brings in extra results that an audio search might not find. Also keep in mind, some people incorrectly name their files which includes mis-spellings, so keep that in mind when brain-storming for search possiblilities to find the file you're after.
Check these if you have time: See the following link & follow “ALL” the off-shoot links to find hints & extra skills to help solve your problem:
To continue files downlding (click on link) & also this tip
Cant search well help