To my bad luck after waiting for almost 21 days to get v 15.6 approved at Mozilla review queue it still got left with a bug and I had to submit a new v 15.7 to fix downloads for all videos. I had requested mozilla to expedite the review for this version. Version 15.6 will allow downloads for 40% of the videos, pls. wait for v 15.7 in next 48 hours.
A fix v 15.6 for downloads stuck at "Pls. Wait" message is now fixed pls. update from here - https://addons.mozilla.org/en-US/addon/easy-youtube-video-download/
If you are having trouble related to PRO activation, pls. follow the guide here - http://youtube-downloader.uservoice.com/knowledgebase/articles/1916182
Use the form below for contact, support and reporting bugs.
Make sure you have followed all the troubleshooting instructions as described above and here https://youtube-downloader.uservoice.com/knowledgebase, send your addon version, format you are trying to download and error/issue details :