There doesn't seem to be a board covering my Samsung Galaxy A51, so I have posted here. Is this OK, or should I post on another board?
If this board is OK then my problem is as follows:

I purchased this Samsung Galaxy A51 mobile about 2 1/2 years ago and up to now it's been working fine. Then yesterday it suddenly stopped and appeared to go into a reboot mode where it displays the usual Samsung reboot picture/logo. I assumed that it was rebooting either because there was a system update to be done, or that somehow I had accidentally started the reboot myself.  Anyway, it stayed showing the usual Samsung logo and I waited for it to move on to the normal reboot procedure. However instead, after a couple of minutes or so, the screen went blank. I wasn't sure what this meant, but I was expecting it to light up again for a reboot/system update/restart, but it didn't. I thought maybe I should press the power button (or a combination of buttons) to power up the device, but nothing happened. Since then it has now stayed with a blank screen and not woken up at all.
My question is: what does this mean and what do I need to do to startup the device again? Certainly, I have it attached to a power supply cable, so there's no question in terms of it having lost power. This is an important device for me and I urgently need to find a way of starting it up and using it normally as Ive done since purchase as new. Can anyone please help solve this mystery?