If the GMass buttons have disappeared from your Gmail account in the last 36 hours, it’s likely because Chrome has disabled the GMass extension due to a mistaken permissions change. To fix this, go to Chrome –> Preferences –> Extensions, and re-check the box next to GMass.
On Wednesday evening, we pushed a new version of GMass to the Chrome Web Store, and this version listed “www.dev.gmass.co”, which is our development server, as a website for which the extension required permissions. Because the previous version didn’t request this permission, Chrome may have disabled GMass because of the new permission request. We have now pushed a fix for this to the Chrome Web Store, so that the latest version does not require permissions to our development server.