First of all, users will need to make sure that their Chromecast device and their mobile device are on the same Wi-Fi network. It never hurts to check that first, majorly if you use more than one network. This case applies whether you have a TV with a built-in Chromecast or a Chromecast dongle.
One more thing users must check is whether both your mobile device and the Amazon Prime Video app got updated to their recent versions. Any missed updates could lead to incompatibilities. Another thing worth checking is that the Prime Video app will only show the cast icon if users are using it from a permitted region. This scenario indicates that users might run into some problems if they have to use a VPN to access the Prime Video service or if they are trying to get into a banned library in their area.