You may need to power on the AVR and then the TV (or vice versa). If they are both on, and then you turn one of them off and back on, it should still work, but that is not always the case.
In any event, two possible causes come to mind. One of the devices is faulty or more likely you are experiencing an HDCP glitch. You can try replacing the HDMI cable, but more than likely it's just an issue that you will to live with.
In any event, two possible causes come to mind. One of the devices is faulty or more likely you are experiencing an HDCP glitch. You can try replacing the HDMI cable, but more than likely it's just an issue that you will to live with.