Account Transfer Forbidden

As the current Account Owner, I need to transfer the Account Owner role to another user (that has been added within the ShinyApps UI) but when I enter the email to make the transition, I receive an error saying "Forbidden" with no addition information. (Screenshot for reference)

Screen Shot 2021-08-31 at 1.17.41 PM

Has anyone else had to deal with this? Would love to understand how you may have been able to solve this, or perhaps it's a bug within the UI.