After this issue, I can't download you tube, vimeo, or any other media. Not even the videos I've previously downloaded.
I've tried to reinstall, tried to unregister and register again.
Have you rebooted your Mac at any point? That could reset your system and help get things back to normal.
If that doesn't help then you are probably at the point where you would want to try a full reinstall.
What you will need to do is delete the app (uninstall) from Applications instead of just reinstalling over it. Then in Finder go to the top menu and then access Go > (holding one of shift/alt/control/command) Library > Application Support > Jaksta Media Recorder and delete that folder (NOTE: doing this will erase your library file list in Jaksta, but your downloaded/converted files will remain intact in their destination folders). Reboot the Mac and then do a reinstall of the latest version (https://www.jaksta.com/download/mac/jaksta-media-recorder) and it will generate a new copy of the deleted folder and the application files.
Let me know if the problem continues.