As a first step that resolves many common problems, close the YouTube app or browser window and reopen it. Next, try restarting your device.
Re-download videos on brand new devices
Check that your membership hasn't expired
Make sure your YouTube Premium membership has not expired.
In the YouTube app, tap your profile photo 
If you recently lost access to YouTube Premium and re-subscribed, it will take a few hours for saved videos to show once you've re-subscribed.
If you need to watch a video right away, tap Menu 
Check that you're signed into YouTube Premium
Make sure you're signed in to the Google account associated with your YouTube Premium membership. Keep in mind that this account may be different from your Apple ID.
- Try signing out and back in to the account associated with YouTube Premium.
- Check that you see the YouTube Premium logo (instead of the YouTube logo). In the YouTube mobile app or on your computer, you should see the YouTube Premium logo in the top-left corner of your app or browser.
- Make sure you're signed in on your TV to the account associated with your YouTube Premium membership.
- If you're casting to TV, make sure you're signed in on both the TV and the computer or device you're using.
- If you're using Google Home, make sure you're signed in to the correct account in the Google Home app.
Contact support & submit product feedback
If you're still having trouble, contact support. When contacting support, mention the following:
- Do you see an error message?
- Where does it show and what is the exact text? Include a screenshot, if possible.
- You can also submit feedback about your issue. You won't get a response, but your feedback will be shared with YouTube.
- To send product feedback, select your profile photo
Feedback
in YouTube.
- Make sure to check the box for "System logs" to help us better understand your issue.