You could have several problems. Let's hope it is simple.
1. The ECU can get confused. If you shut the unit off with the 3 point in one positions (let's say "up') and some one either A. moves the sliding lever (on the armrest I think) that that controls lift arm height, or B. lets the arms down while the tractor is not running (or the leak down, neither situations happen often), the the ECU senses the 3 point arms in one location, but sees the lever in another and flashes the light (and stops the lever from working). Same thing can happen if you have the key "on" (no running engine) and you move the lever. Basically, get the 3 point all the way to the bottom, set the lever all the way to the bottom, shut the tractor off and restart it and see if that helps. Also, check to make sure the knob that sets your "upper travel limit" of the 3 point arms is tuned to the "max" setting. If the arms are left up and this knob gets turned while the engine of off, it can confuse the ECU (the arms are above the upper limit and the ECU does not know what to do).
2. Bad wiring or ECU. The cab controls go through the ECU before going to the 3 point solenoids. The buttons on the back give straight battery voltage to the solenoid. The buttons on the back will work no matter what is wrong with the ECU or cab wiring (as long as the tractor will run).
These explanations are a little over simplified, but the principles are sound.
