DIAGNOSIS Weak or unstable 2.4GHz Wi-Fi signal at the dishwasher's location. The module has a basic antenna.
FIX In the SmartThings app, delete the dishwasher. Perform a factory reset on the dishwasher: hold 'Heated Dry' and 'Delay Start' for 10 seconds until it beeps. Reconnect it, placing your phone right next to the dishwasher during setup.
IF THAT DIDN'T WORK Your router may be using a Wi-Fi channel that conflicts. Log into your router and set the 2.4GHz band to use channel 1, 6, or 11. Avoid auto-channel selection.
HEADS UP The dishwasher does not support 5GHz networks. Ensure you're connecting it to your 2.4GHz band. Mixed networks often cause setup failures.