Looks like the token expiry timestamp is about an hour after the app was built (or 50 minutes?). So I suppose the web site is just not generating a new token when you try to download the app.
Hi. It looks like on the internal build page url to the artifact is cached, so after you open it once, the next visit is using signed URL that was generated a while ago(and url is only valid for 15 minutes).
You can workaround that by clearing browser cache on expo.dev.