When in a Zoom conference and using the "Share Screen" function. You need to keep in mind of what application or window you are sharing. For Microsoft Office PowerPoint, this gets a little weird. So here is how to share a PowerPoint correctly.

First step is to click Share Screen, this icon in fact: 

Once you click that icon, it says at the top "Select a window or an application that you want to share". Zoom will detect what windows and applications you have open in the background, if you don't see the window or application you want to share then it is not open. For example, if you want to share your web browser like Google Chrome, you need to have it open in the background otherwise Zoom won't see it and therefore can't share it.

You can see we have two windows of PowerPoint.

The first one indicated here, is when you full screen your PowerPoint also known as Fullscreen Mode.This is what you want to share when you want everyone's focus to be on the PowerPoint.

Note: That when moving to a different window or application that you are NOT sharing will cause the share screen to pause, it does this as a means of privacy for you so you can look at an email or something while everyone just sees the presentation until you come back to it (by clicking back into that window which makes it "active" and Zoom sees that so it will continue sharing). Sharing your Desktop 1 does not do this so be mindful that everyone sees what you sees in that mode.

But what about this one?

It will share exactly