2004 FX140

I removed repaired and replaced the engine. Now the multifunction display will not work. I have swapped out the entire wiring harness including ECU, and the display and even the stator. When I purchased it the motor was frozen solid. Pressing the start button would sound the buzzer and the display would come on momentarily. Ski starts and runs now but no buzzer or display. Any ideas of what to check?

Merry Christmas