If you're experiencing posting failures to Youtube, with the error "The authenticated user doesn't have permissions to upload and set custom video thumbnails", there's an easy way to fix this!
First, you'll need to add a phone number with the Youtube channel following this link here
This will unlock custom thumbnail permissions for your Youtube account
Once you've verified your number, you'll want to just re-add your Youtube account again to Cloud Campaign. You can find steps on how to do this in this article here
If you continue to run into any issues after completing these steps, please reach out to our support team, or review the additional information on this resolution here