This is actually pretty common with a lot of remote software and is not limited to simplehelp or the OS version.(linux,windows mac, all affected ) A request to support may be appropriate. They may be able to include a workaround in a later version if enough people request the ability to control the machine of a headless desktop.
For now, you will need a dummy adapter for monitor emulation if you want to run headless.
Here are 2 examples:
https://www.amazon.com/Headless-Display-Emulator-Generation-Single/dp/B07FB8GJ1Z
https://www.amazon.com/EVanlak-DisplayPort-Headless-Emulator-3840x2160/dp/B07YLP1GG4