If you are unable to add a manager to your YouTube brand account, it’s possibly because you are logged in as a manager, instead of being logged in as an owner. In the examples below, you’ll see that the icon is missing unless the person currently logged into Google is the owner of the YouTube brand account.
So the solution is easy:
- Log out of gmail, then log into gmail using the account labeled “owner” or “primary owner.”
- Then visit this webpage: https://myaccount.google.com/brandaccounts
- Then select the brand account from the list.
- The “invite new users” icon should show up.