Update: YouTube is back and working again for the large majority of people! If you're still seeing an issue, it should be fixed soon.https://twitter.com/TeamYouTube/status/1135271882985312256 …
That's odd! What device are you on? If you're on a browser, try clearing the cache and cookies. If you're on a mobile device, try these steps: delete the app > restart your device > reinstall the app. This usually clears things up but let us know if it's still not working.