My 642 stopped making ice; I took the and cover/rear plate off so I could see what was happening ice-maker-wise. I saw no water in the maker. I realized a plumber had (possibly; I'm not 100% sure) turned off what i believed was the water supply to the freezer. I turned that on, but still do not see water filling the tray maker. Any ideas?

You may have an ice plug frozen in the fill tube, for that use a hair dryer to try and unfreeze the ice plug. Be sure the mechanism is actually working. A clock mechanism rotates a cam on the front of the icemaker that hits a micro switch for a period of tme that operates a water solenoid. That solenoid pulls a plunger valve out of the water line, allowing water to flow up to the icemaker. When the cam pulls off of the microswitch, it interrupts the power to the solenoid. The plunger snaps back in the line due to a spring compressed on the first operation. If that solenoid is not getting power, then the water does not flow. The Ice full bail operates another microswitch that stops the clock mechanism from operating. If the tang on that microswitch is broken, then nothing happens.

You are going to have to determine what part is defective, the solenoid or the ice maker itself. The ice maker is the easiest to replace as it is connected by a plug and a couple of screw clamps holds it in place.