SMG - TV Displays "Mode Not Supported" Error Message
Confirm that the device connected is outputting a supported resolution.
The resolutions that the TV supports:
480i/p (640 x 480)
720p (1280 x 720)
1080i/p (1920 x 1080)
2160p (3840/4096 x 2160)
Power Cycle the TV and the external device.
Turn off the TV and the external device,
Turn the TV on, and wait about 15 seconds.
Turn the external device on.
This tests the HDMI "Handshake" between the two devices and confirms that it is being done properly.
Try using a 6 foot or shorter HDMI cable.
Long HDMI cables can sometime cause an issue resulting in a "Mode Not Supported" message. If a cable longer than 12 feet is needed be sure to use an ISF rated cable.
Set external device to a fixed output resolution.
StepComponent Content
Try another HDMI device using the same resolution.
If the TV is able to function with a secondary HDMI device at the same resolution, this is an indication that the TV is not the source of the problem but the signal being sent from the original device.
Update the Software on your TV
Performing a software update on your TV can add new features and correct bugs that are occurring. See Samsung's guide for Updating the Software on your TV.