Check the cable connection - make sure the cable connects to both sides firmly, if your cable does not fit properly get your HDMI cable locked.Try opening things differently - when you first turn on the TV and other devices behind the TV and reverse the order to unlock the devices. also mentioned in connectivity FAQs.
Use a different HDMI input: Switch to another TV input and back to HDMI and see if the signal locks are correct.Look for firmware updates- See if there is a firmware update available for your TV, if yes then install the update.Remove devices - unplug any existing intermediate devices and connect the HDMI connection directly to the TV, when the connection improves the intermediate devices causing the problem.