Does the cab cvf file you are using having a working sunflower?
CabSignalDisplay ( Type ( ASPECT_DISPLAY CAB_SIGNAL_DISPLAY ) Position ( 600 79 40 40 ) Graphic ( aws.ACE ) )
The AWS ace having the two states.
I ask because some cabs either do not include that part in the cvf file or do not include the graphic to go with it.
Also check Carlo's instructions - I think it is still in latest version of Monogame only.
Finally the sad news that at the moment it seems unable to apply vacuum brakes.