Share screen - participants' camera appear in black on my screen

Hello guys. I'm having a problem with zoom.

Every time that I share my screen (choosing an specific window), the window that shows the participants gets in front of their screen(black) and they can see clearly what I've shared.

And when I'm sharing, If I alt+tab, appears a orange border on my screen and it blocks the file that I decide to share with them.
What can I do to solve it?
Thank you very much for helping me