In the latest Zoom update they have introduced a rather silly default which may catch Zoom users who do screen sharing. In previous versions you could share your whole desktop screen quite easily. Now, in the latest update it switches that off! So you are restricted to sharing applications only. This will catch people out and may catch you out.
It’s a simple matter to switch it back on. Go to Settings, and half way down basic settings you will see the option to switch off “Disable Desktop Screen sharing.” Why on earth it hasn’t set the other way round I don’t know!