youtube video downloader doesn't work always

I have two accounts n Youtube and the same video downloader app installed. in the first account I cannot download any video and i get the message "no links ere found". if I switch to the second account in the same video, I have no problem and I do download the video. what can be the solution to the problem?

I installed the extension with the first account which I use as the primary one. at the beginning and for a few months it worked fine and suddenly it stopped working. I didn't do anything. I changed to the second account for other reasons, and I noticed that the downloader works without any problem.