If you see an error on your Apple TV that says
Already playing another movie. (145)
It typically points to information stored on the device that needs to be refreshed. Follow the troubleshooting steps below to resolve the issue.
On a different device using your account, stop playing Netflix or close the Netflix app. If you don't know which devices on your account might be playing Netflix at the same time, you can check which devices recently watched.
Or, upgrade your Netflix plan to allow more devices to watch at the same time (up to 4 with the Premium plan).
If your Netflix account is being used without permission, you can stop someone from using your account.
Turn off your device. If your device has a power cable, unplug it.
Make sure your device is completely off, not just in sleep or standby mode.
Leave your device off for 15 seconds.
Turn on your device and try Netflix again.