It might happen sometimes that when you try to cast a video to your chromecast all you will is just orange loading bar and nothing else, after some time stremio just stops casting. It happens because your firewall is blocking chromecast. To fix this issue you have to remove blocking rules.
1. Go to the windows firewall
2. From Actions Select Restore Defaults
3. Restart Stremio. There should be firewall notification asking you, if you want to allow connections from node, accept it.
5. Now chromecast should be working