2. Check the solder joints on the diode - if the diode is loose, part of your row may register, while the other may not.
3. Check the solder joints on the columns - if your column wiring is loose, part or all of the column may not work.
4. Check the solder joints on both sides of the wires going to/from the Teensy - the wires need to be fully soldered and connect to both sides.
2. Check the solder joints on the diode - if the diode is loose, part of your row may register, while the other may not.
3. Check the solder joints on the columns - if your column wiring is loose, part or all of the column may not work.
4. Check the solder joints on both sides of the wires going to/from the Teensy - the wires need to be fully soldered and connect to both sides.