If you regularly use Firefox Aurora and Firefox Nightly it happens once in a while that add-ons become marked as incompatible. To enable those add-ons, follow these steps:
- Install the add-on Nightly Tester Tools (you don’t have to run Firefox Nightly to use it) and restart the browser.
- Now click the menu option Force Addon Compatibility under Tools > Nightly Tester Tools.
- Restart the browser and you should be able to enable the add-ons that earlier were incompatible.