When parental controls are enabled on your iOS device, then “Screen Recording” is restricted by default. When “Screen recording” is restricted, you will not be able to start screen mirroring from your iPhone or iPad device to TV. Thus if you have parental controls enabled on your iOS device, please make sure that “Screen recording” is not restricted, to be able to mirror your iOS screen to the TV.
Please read the instructions below on how you can turn OFF restrictions for Screen Recording on your device.
If you are on iOS 13, go to Settings > Screen Time > ‘Content & Privacy restrictions’ → Content restrictions. Scroll to the bottom and you will see an option called ‘Screen Recording’. Set ‘Screen recording’ to ‘Allow’.