We'd like to know more. What device are you using? Do you see the same happening across devices/browsers? Also, please share screenshots with additional info for us to understand this better. Thanks.
We have the same problems. If we change a private video to unlisted, it gets recognized by the youtube data api and our api calls with php work normal. Without that change we get 404 errors (video id not found) since arround 10:15 UTC+1 today.