At the moment we haven't been able to find a solution with Google to why some accounts are not showing all account and/or videos.
Only way to fix this issue at the moment is to create a dedicated new account for this purpose and login in sidebar to YouTube data source with that as well.
1. Create a new Google account for this purpose.
2. Go to Creator Studio Content Manager for that particular account that you are having difficulties with and create a new user:
3. Create the new user as administrator (use the Google account you created earlier):
3. Open up the invitation email from that new Google Accounts Gmail and from the email that you received from YouTube, click "Visit the sign-up page to accept the invitation":
4. Select "Use existing Google account":
5. Select the new account you earlier created
6. Go to Supermetrics sidebar, and add a new account:
7. Select the account you earlier created
8. Go to "Select channels/videos" in the sidebar after the login is completed and you should see everything in the account/videos list:
