Used this add-on for years and was disappointed to see that - as with others that I like to use - the add-on ceased to function correctly following the recent FF update. At least the developer is interested and by all accounts is sorting out what needs to be done to get it working correctly.
Its not a disaster - FF still works and there is a solution coming and what's more IT'S FREE - (unless like some of us you choose to contribute a few $).
To those who have berated the developer I say - cut him some slack - give him time and thank him when he has produced a solution!