My K3 did the same this morning. I charged it over night and this morning the light was still amber, but that's nothing new, it's always done that every now and then for over 2 years. I unplugged it and brought it to work like I always do, went to turn it on and got no change on the screen. I held the power button for over 20 seconds, after about 7 the green light quickly came on and went off again. Still got nothing when I let go of the button.
I put it back on the charger and after about a minute it started to reboot, the Amazon page popped up and the loading bar showing the progress. It took over a minute to finish rebooting and finally the screen came on but there were no books, just empty collections. The screen flashed again and now all my books show up. I didn't touch anything and let it go back to sleep. I still have it on the charger now and the light is still amber after 2 hours (plus 8 from last night).
My question is, do I leave it on the charger without touching it until the green light comes on? What if it never turns green? I'm just scared I will mess it up even more if I pull the plug too soon.
Any advice...besides swapping the battery?
EDIT: The green light came on after 4 hours, I unplugged it and it seems to be working again