So i saw a lot of posts here about the error which i also had today and the method of clearing cached images and files, cookies didnt work…
So this is the alternative quick fix
By default, while you click on sign in, youtube will go to this url
https://accounts.google.com/ServiceLogin?service=youtube&uilel=3&passive=true&continue=https%3A%2F%2Fwww.youtube.com%2Fsignin%3Faction_handle_signin%3Dtrue%26app%3Ddesktop%26hl%3Den%26next%3D%252Ffeed%252Flibrary&hl=en
If you are having this error, while you click sign in, yt will be always redirecting you nowhere except youtube.com/oops
So to fix this error, manually modify the url and hit enter
Visit this altered link instead
https://accounts.google.com/ServiceLogin?service=youtube&uilel=3&passive=true&continue=
this will take you to your google accounts page and auto open this panel
click the youtube icon, you will be redirected to yt, now click on the lock icon remove youtube cookies and reload the page… you’ll be signed in.