I am currently creating an application for personal/internal use only that will help me upload and manage youtube videos on a number of brand accounts I have. Due to the internal nature of the application, I have listed the User Type on my OAuth consent screen is "Internal". I have set authentication up using OAuth Client ID and this works as expected for my main account.
However, when I attempt to use the same application for a brand account associated with that main account the authentication failed with the error "Error 403: org_internal" stating "This client is restricted to users within its organization.". The brand account I am trying to use is owned by the main account for which the authentication works and so I would expect this brand account to also belong to my organisation and therefore be able to use the application however this doesn't seem to be the case.
Is there something I can do to make my application work with this brand account, or some way I can associate my brand account with my organisation so that this works. I really don't want to have to go through verification for an external user type as this requires websites, privacy policies, terms and conditions and even a video detailing how the data will be used, which is massively overkill for an application I just want to use on my own personal account.
Thanks.