Hi,
Have you updated the device to TVOS14? I am unfamiliar with the 3rd generation as I do not own it but a google search bought up this:
tvOS 14 Compatibility List
Here’s a list of all the Apple TV models that are capable of running tvOS 14 officially when it comes out, as confirmed by Apple on their website. Although there aren’t many models to cover, if your Apple TV is several years old, there’s a fair chance that it will not support the upcoming version of tvOS.
Apple TVs Compatible with tvOS 14
- Apple TV HD (4th generation)
- Apple TV 4K (5th generation)
Unsupported Apple TV Models
- Apple TV (1st generation)
- Apple TV (2nd generation)
- Apple TV (3rd generation)
If your device doesn't support TVOS 14, it could be YouTube has dropped support for it too. To check this information as I'm not 100% sure, please contact YouTube and they'll be able to confirm.
Sorry I couldn't be more help on this
https://support.google.com/youtube
[Personal Information Edited by Moderator]