Hi there and welcome
Sleep mode is when it powers down after a set time but using the remote will wake it up again, so this is not the cause.
Can you please remove the power to the unit (so unplug it from the power socket).
Then wait 10 minutes, connect the power again to it, turn it on and tell me please if it is now operating correctly.
Let me know the results please
ok, remove the power to it, then hold the power button in and with it held in, connect the power
What then happens?
It is the internal mainboard that has faulted, it will be the memory on it and it is not able to read the firmware to start
I am really sorry about this and you are going to have to return the unit to have it replaced. It will be covered by the warranty if this has not expired, and the replacement will be done at no cost to you.
I am really sorry about this, and if you have problems, or would like any additional information or assistance, please do not hesitate to let me know.
And if you can take a second to rate my service by clicking one of the stars at the top of the page, then submit, that would be greatly appreciated.
It is the mainboard that has faulted, a repair store would have told you the same thing for a lot more, and then offered to replace it and I can tell you in my experience its more expensive in the long run as the repair and parts will be minimum 150, with a short term warranty (most offer 3 months) . It is something I would avoid.
I am sorry you felt dissapointed with the info, but I can only tell you the situation and what has caused this and what needs to be done....