Screen Sharing

While in zoom meetings...

1) I am Host, and I want to share my presentation. Atendee/ Invitee cannot see it in her screen.

2) When atendee/ invitee wants to share her presentation, an error message pops out, reading "it is not possible to share screens. Try again later. "Error code: 0".

What do I do, just so atendee/ invite can see my presentation and she can share hers?