Try the steps first.
It may or may not work for you.
- Logout from youtube.com
- Close the youtube tab.
- Open a new tab and go to brave://components and click “check for updates” for all components. Make sure the components are all updated.
- Go to brave://settings/content/all
- Search for “google” and delete all cookies related to google
- Search for “youtube” and delete all cookies related to youtube
- Close and reopen your brave browser.
- Login to youtube again. You are good to go.
If it does not work, you may have to disable brave extensions like Enhancer for youtube. Check any extension settings to see if you have any adblocking enabled. Disable them.