Mozilla made some changes to way add-ons were deemed ‘compatible’ back in Firefox 10.If an add-on is hosted on AMO and met certain criteria (see below) then the compatibility would automatically be ‘bumped up’ to the next Firefox version. Because of this, the Addon Compatibly Reporter can no longer be used to force add-ons to work (though it can still be used to “report” compatibly status). Brain King, the author of the Add-on Compatibility Reporter extentions explains:
Compatible By Default does not enable all extensions. The types not enabled include the following:
- Add-ons marked to work with a Firefox version less than 4.0
- Add-ons with binary components
- Add-ons explicitly marked by the author as incompatible, i.e. opt-out of Compatible By Default
- Add-ons tested and determined to not be compatible with a given version of Firefox, and marked as incompatible by Mozilla
So for those add-ons that meet any of the 5 exceptions above (or not hosted on AMO) you can still force them to work automatically (at your own risk of course) via the Disable Add-on Compatibility Checks extension. This extension makes the needed changes in about:config for you and takes effect immediately. No restart is needed for the add-on installation, but in order to reactivate the disabled add-ons a restart is needed.