It used to work perfectly, but in the recent one month-ish, everytime I try to cast Youtube from my phone to my TV the phone will be in the "connecting to your TV" state forever until it finally timeout. I can pair the TV's Youtube app with my phone using the TV code and cast, but that way it only works after I already opened Youtube app on the TV (with normal chromecast it can wake the tv up and open the youtube app automatically).
I had this too. Tried unlinking my YouTube account and all sorts without any luck.
Uninstalled all updates for the "Google Cast Receiver" app and it worked. Re-installed updates and it carried on working. Give it a go :)