To use Presentify with any video conference apps, like Zoom, Teams, etc. you have to select the entire screen while sharing instead of a single app (or window) as shown below:
This is also mentioned on Presentify’s FAQ page. The reason for this is that Zoom, Teams, or any other app shares just the window that you choose to. So, when you choose a single app’s window, only that window is shared and nothing else. When you choose the entire screen then all the windows are shared (even Prentify’s invisible window) and its annotations are visible to your audience.