We'd like to know more. What device are you using? Just to confirm, have you tried any troubleshooting steps? Keep us posted.
@YouTube @TeamYouTube unable to add videos to watch later. Get message saying 'Internal Error Encountered' 
-
-
-
It's working now, thank you for your response though. I have no idea why it happened. But I'm glad I could report it
End of conversation
New conversation -
Loading seems to be taking a while.
Twitter may be over capacity or experiencing a momentary hiccup. Try again or visit Twitter Status for more information.