You may run into this problem because of your Smart TV firewall settings. To fix Disney Plus Chromecast not working error, you will need to allow incoming connections for casting titles to the TV. Here’s how you can do it:
Go to your System Preferences.
Select “Security & Privacy” and click on Firewall.
Select Firewall Options and uncheck the box beside “Block all incoming connections.”
Then check the box next to “Automatically allow signed to receive incoming connections.”
Now you can start screen mirroring Disney Plus to your TV.