Hello, few days ago my gallery rss feed (to my website home page) just stopped working, I've made no changes or additions to the gallery or feed codes for months.
Checked the feed on other feed widgets and the feed doesn't work on them either, so obviously the problem is with the feed itself for some reason. Can't find any info on this in search or troubleshooting.
Any suggestions for troubleshooting this?

You did not provide any specific info. Please take a look how to report bugs properly so we can help:
http://www.zenphoto.org/news/general-contributor-guidelines#reporting-bugs

Zenphoto Version 1.4.5.9 (official Build)
Default Theme
php version 5.3.28
MySQL version 5.1.73
Web site www.fishnbc.com
(note: the feed was displayed on the home page "latest images from the fishn'bc gallery")
gallery www.fishnbc.com/zen
browsers - all

I would guess that you recently reset the mod_rewrite option. The issue appears to be an ampersand in the URL to the images. These are query parameter links rather than rewritten ones.

Seems there is a bug in 1.4.5.9 that does not properly encode those links. It is fixed in the 1.4.6 BETA or you can enable mod_rewrite.

Thanks sbillard, I enabled mod_rewrite and it fixed the issue.