Diagnosis
The three-beep alert is a door switch error. The control board isn't detecting that the door is fully latched.
How to Fix It
Open and firmly re-close the door. Listen for a solid click. Check for any utensil or dish blocking the latch. If it persists, inspect the door latch assembly. The plastic latch hook can crack. You need to replace the whole latch assembly, part number W10773850.
If That Didn't Work
The door switch itself could be faulty. It's a small rectangular component behind the lower door panel. Unplug the dishwasher. Test the switch for continuity with a multimeter when the latch is engaged. Replace the switch if it's open circuit.
Heads Up
Never bypass the door switch. The dishwasher will not run, and it's a serious safety hazard. The door must signal as closed for the fill valve and pump to operate.