I have notice that after upgrading Kodi the youtube add-on for trails do not works any more ,and all videos fail with “The following content is not available on this app” , and some other errors .
The solution I have found is to replace a file called “video_info.py” . I think there is more then one solution but the simple one is :
replace : video_info.py at this location: C:\Users\ (your user)\AppData\Roaming\Kodi\addons\plugin.video.youtube\resources\lib\youtube_plugin\youtube\helper
And thats it !
you can download this file from here
Good Luck