My extension's update.json isn't working; how do I troubleshoot it?

 "applications": {
   "gecko": {
     "id": "button@booktrakr.com",
     "update_url": "https://www.booktrakr.com/uploads/downloads/firefox-updates.json"
   }
 },

manifest.json has: "applications": { "gecko": { "id": "button@booktrakr.com", "update_url": "https://www.booktrakr.com/uploads/downloads/firefox-updates.json" } }, When I try to load the update_url in my browser, it works fine using the URL quoted above. My update file looks like: { "addons": { "updates": [ { "version": "0.3.3", "update_link": "https://www.booktrakr.com/uploads/downloads/BookTrakr%20Button%20for%20Firefox.xpi"} ] } } If I copy that URL into my browser, it downloads the file, so the URL seems to be correct. When I try to force an auto-update, FF appears to look for an update, but nothing installs and my extension remains version 0.3.2. Can't find any help on how to troubleshoot this situation. Can someone suggest some techniques for troubleshooting or point me to a blog post or something?