Publishing videos to Facebook Page as Page - publish_stream and manage_pages permissions not working

Attempting to write a simple server-side Python script that posts videos to a Facebook page (not a personal page, but a sports team page that I have admin permissions for). The script works perfectly when uploading videos to my own personal FB page, and other FB pages that I created — but I keep getting this error:

OAuthError: [200] (#200) Subject does not have permission to post videos on this page

When attempting to post videos with the script to a page that I do have admin permission for, but I didn't create (pointing that out because it's a consistent difference in the oauth response I keep seeing, assuming maybe page creation has something to do with this?).

I have tried using facepy, which is a great Python library for Facebook, but so far no luck in resolving this issue.

I know that responses to questions related to this topic from a few years ago mention that:

To publish to Page as User you need publish_stream permission granted by User.

To publish to Page as Page you need publish_stream and manage_pages permissions granted by User and Page access_token which can be retrieved from accounts connection of user.

But when creating a token for my app using Facebook's Graph API Explorer, all of these permission are enabled/checked off, every single one, but still the same permissions error.

Has anyone seen anything like this?