@TeamYouTube I am having a repeated issue where a select few channels I am subscribed to suddenly have notifications turned off whenever I watch one of their videos or click on their channel and when I turn on notifications again the next time I return they're off again.
There are no related technical issues. It could be possible that your account may be logged in multiple devices. If yes, signing out from all devices and signing back in may prevent this from happening again: https://goo.gl/84MFdo . Let us know if this helps.