By default, Promote Control assumes your camera exposure mode is set to "Manual" whenever you connect it to Promote Control. Change this setting to "Yes" to tell Promote Control to use the USB connection to reset your camera exposure mode to "Manual" when Promote Control is connected. This feature is disabled by default because it is not compatible with all cameras.
On some cameras, including Canon 5D Mk II, 5D Mk III, 7D, 60D and some others exposure mode may only be set with a manual dial and cannot be set electronically. If Promote Control fails to change your camera exposure mode, it displays an error message and you should return this setting to "No".