HDMI pulpit input won't display via Webcast

We have a newer stake center with the HDMI video distribution system in the building. Everything works well. We can switch between the chapel camera and the pulpit input to display on all of the screens in the building. The camera input displays on the webcast fine, but when we select the pulpit input the image from the PC for about 10 seconds and then it changes to a green screen. When we go back to the camera it displays correctly. Is there a reason why we can't display the screen from the pulpit input over the webcast?

My guess is that the image from the PC isn't compatible with the what you're using to view. Some combination of resolution, frame rate, interlace/progressive, etc.