Hi,
Have someone who is a global administrator or someone with Stream admin permissions login to the stream portal at web.microsoftstream.com and then go in and go into discover.
Video should be there to which you can assign permissions.
Let me know how it goes. The person who uploaded the video - she should also as the owner of that video log into the stream portal, go to my content and then the video should be there which she can edit and apply the permissions to other users or set to companywide.
Hope that answers your question!
Best, Chris