YouTube Password

I've been downloading videos from Google for many years, but somehow it seems that I can no longer do so for certain vids until I insert my email address and password. I assume that refers to the info I use to login to Google, since YouTube supposedly uses the same info. However, when I enter that info for a video YouTube will not accept it and stops the download immediately. No matter how many times I try with certain videos the email and password is not accepted in You Tube. It does seem that the email address is accepted, but it still asks for the password. Any ideas what's happening here and perhaps a fix.