Trying to use this sample app provided by Google: https://github.com/googlecast/CastHelloVideo-ios
It is not asking to connect with my Chromecast, or even scanning for receiver devices. There is only the "Cast Video" button that alerts "Not Connected - Please connect to Cast device" when clicked. I understand there is a whitelisting/registration process for styled and custom media receiver apps, but there is supposed to be a default media receiver app built into the Chromecast that I should be able to use right away. How can I make it scan for devices?
Did you follow the instructions for setting up that app? Unless you use your own App Id or you update the sample to use the default app id, it won't find any device; it is doing the scanning. In addition, please use the GitHub's issue tracker to ask questions about that and other cast samples if you run into any issues when trying to run them.