Rated 5 out of 5 stars

I'm going to assume this is Stylish's fault, but userstyles will only update through the Add-ons Manager. Is there a workaround for this issue?

This review is for a previous version of the add-on (2.3). 

I didn't know it was broken. I don't use Stylish. I looked in to the problem. Stylish stores its ids as numbers (integers in Javascript.) Firefox looks for "strings". I now convert them. The fixed version is posted now, but not reviewed by Mozilla yet. You can click the "Version Information" link at the bottom of this page and then click on "Version 2.3". It will take you to a page where you can get version 2.4, or just wait a few days for Mozilla to approve it and it will show up on the main page here.