4X4 and front wheels are not engaging.

I want to diagnose why my front wheel's are NOT engaging when I shift into 4H or 4L. I took the skid plate off protecting the actuators and sprayed carb cleaner to get a good look and all hoses were fine and the 2 electrical plug-ins were fastened. I'm hoping to get lucky and I am trying to locate any fuses or relays that I can check. I'm afraid it's one of those actuators and I couldn't see how they unplugged. I am blind in the right eye. Any advice is appreciated. I have no way to check voltages or vacuum.