I provided some pages of technical information in the images below that may help you diagnose and repair this console problem in your treadmill. The first 3 images show the information on that MC-2100 controller. Your details indicate that you may already have that information. The 4th image shows the wiring diagram for the treadmill. The 5th image has a troubleshooting flow chart. The final 3 images have the information for your console. Be sure that you
unplug the treadmill
when accessing internal components. Some of the technical information provided below describes live voltage checks. If you conduct live voltage checks on the treadmill, be sure that you
wear electrical safety gloves and safety goggles. Unplug the treadmill as soon as live testing is completed
. Your details seem to indicate that you are comfortable with examining and checking the internal components of the treadmill with it plugged in. Some of the checks involve low voltage DC measurements. Be careful not to contact the 110 volt components when making live voltage checks. If you get to the point where you need to have a service technician diagnose and repair this failure, you can schedule service through this link:
Sears Home Services
There is a large amount of technical information provided below. I recommend that you attempt to enter the Calibration Mode first. If you are not able to enter that mode, I recommend that you check the wiring connections between the controller and the console (you probably already did that). The next step would be to check for DC voltage going to the console from the controller. If the console gets DC voltage but will not power up, then it will need to be replaced.
You can order parts from this page:
Proform Crosswalk 400e Model 831.296330 Parts
I hope that this information helps. If you need more assistance, reply with additional details based on the results of your tests.