when on desktop meeting, i can't share my phone screen

Hi,

during meeting on desktop zoom, I was going to train on a software and its app. Sharing screen on the computer was just fine.

I joined the zoom through my phone too and wanted to share screen of the phone, clicked share, clicked screen.

Phone has green sharing line 

Desktop screen says the phone has started screen sharing, but the screen is black.

I have allowed zoom within the settings, but now I don't know.

The phone took over the running the meeting too, that didn't help either. 

this is Samsung galaxy 21.

thank you very much for any help