Clara HD Kobo Clara HD stuck on sleeping screen

Hi all, I have Kobo Clara HD that is stuck on the sleeping screen. I suspect the battery must have died while it was in sleep move. However, I've tried charging it for several hours and the screen is still frozen.

I am not able to turn off the kobo and the manual reset doesn't do anything as well, the screen remains frozen in sleeping mode. Has anyone else had the same experience / ideas on how to resolve this?

Thank you!