Edit: Adobe has approved the 3.4.7 update. This is no longer necessary. If you are having issues installing via Adobe Add-ons, please see this guide.
I’ve been receiving a lot of reports of GuideGuide not working in CC 2015.5 for people that purchased through Adobe Add-ons. Today I discovered that it’s my fault :(. In the packaging process for Adobe extensions, there are two places to specify the installation version range. My automated system was only updating one of those versions, so while GuideGuide will technically install, it will not appear in Photoshop CC 2015.5.
I will be publishing an updated version shortly (4.3.7), however Adobe’s approval process can take a few weeks. If you’re one of the people who currently can’t use GuideGuide because of this, please send proof of your Adobe Add-ons purchase to firstname.lastname@example.org and I’ll send you a download url to get a free copy of GuideGuide through my own store.
I’m quite sorry for the trouble and hope I can get you back up and gridding as soon as possible.