Confusing appid-url-not-reachable

id: io.github.q962.PictureWindow                              // failed
id: io.github.q962._Picture_Window                         // ok

id:io.github.totoshko88.RustConn                             // ok
id:io.github.Geocld.XStreamingDesktop                 // ok

I don’t know either. This really confuses me.

The ID formats are all the same. The corresponding GitHub repositories all exist.

Why is it that only my ID can’t be matched with my repository?

{
    "errors": [
        "appid-url-not-reachable"
    ],
    "info": [
        "appid-url-not-reachable: Tried https://github.com/q962/picturewindow"
    ],
    "message": "See https://docs.flathub.org/linter for details and exceptions"
}