All right now.
The screen displays USB icon and led lights in red. I've unplugged the reader and switched it on. Works fine. I will complete the charging.
In the first moments of panic, I had read
https://www.mobileread.com/forums/showthread.php?t=21337, but I believed that first point didn't suit this scenario. So, my apologies to Patricia, and my thanks to her and HarryT.
Will continue reading an learning from you, despite of my problems with language.