The Nook stucked when booting

[cooper.spb]

Hello to everybody
Hope somebody can help me with my problem.
I bought the nook which was previously rooted. In order to restore factory settings I made a hard reset, erasing and deregistering the account.
When pressing the power button i see the picture of the carton box on a white background. The boot is stucked and the picture is starting to flicker.
Switching off/on doesn't help.
what to do next?

thanx in advance!

 

[J515OP]

Power down by holding the power button for about 10 seconds. Then power up again and see what happens. Oh and welcome to the forum.

 

[cooper.spb]

already done - the nook switches on and stucks on the flickering picture with a box.
may be there is another way to reanimate it? disconnecting the battery for some time?