Watch together 'error user has no access'

im trying to use watch together feature, and the person says they get a error saying they have no access

Same issue. I can share out but when the same person tries to share with me, I get this error.

In order to be able to watch a movie/show together, all users need to have access to that video.
Can you confirm you have shared that particular video (or library) with the user(s) beforehand?

Yes. I can watch the video from their library directly just fine. The problem only crops up during watch together.