DIAGNOSIS dC is a communication error between the main control board and the display/user interface board. It's not Wi-Fi related.
FIX Unplug the washer for 5 minutes. Plug it back in. This resets the boards. If dC clears, run a rinse cycle to test. If dC returns immediately, the connection ribbon cable between the boards is likely loose or damaged.
IF THAT DIDN'T WORK A failed control board is the cause. The main PCB (part number DD82-01621A) or the display PCB (DD82-01622A) needs replacement. You'll need a multimeter to diagnose which one.
HEADS UP Do not attempt to re-seat ribbon cables with the power plugged in. You risk shorting the boards.