See the attachment for your tech sheet.

Have you tried pushing the cancel button?
Have you tried unplugging the unit for a couple minutes to see if it will reset?

If yes to both the above then try the following.
Connector Cleaning / Checking
Unplug the unit
Open it up
Remove the ribbon cable from the keypad to the control board at the control board.
Clean the edge connector. Use electronics contact cleaner or isopropyl alcohol.
If it is the type where there is not a connector just the insulation is removed, it can be cleaned with a pencil eraser. Do not use an ink eraser as it is too abrasive.
Check the tracks in the ribbon cable for hairline cracks. A magnifying glass helps here.
Would not hurt to clean the connector on the board. Use electronics contact cleaner or isopropyl alcohol and a tooth brush. Be gentle and do not reconnect till all the solvent evaporates.
Reconnect everything and give it a try.

The problem is either the keypad or the control board.

Unfortunately they do not publish the pin-out for the keypad so it is difficult to check it.

Since the keypad was OK before you had the board repaired then I would say that odds are that the control board is the problem but I do not know how the repair company checked the board out so this is just a guess.

Try checking the receptacle on the control board.
Could be it has a cold solder joint. Cold solder joints are often a duller silver color and/or have pin holes.

You could also try wiggling the connector while watching the solder side to see if any of the pins move in the solder.
A magnifying glass helps with the above.

Looks like the keypad is a sealed system so I do not think that you will be able to check the continuity of the individual tracks in the ribbon cable.