This is the same problem as this : https://itch.io/t/5594887/not-working-in-virtualdesktop
You have to use the button in Tools -> Create a recordable window to be able to stream the overlay. However, you have to hide this recordable window to let Hotscreen see what is visible under the censor. This means that Moonlight/Apollo must have a compositing setting to recreate the entire desktop+overlay.