DIAGNOSIS The dehumidifier's WiFi module has likely lost its connection profile or entered a low-power state. A power cycle at the unit is required.
FIX Unplug the dehumidifier from the wall outlet. Wait 60 seconds. Plug it back in. Once the display is fully on, press and hold the WiFi button on the control panel for 5 seconds until the WiFi icon blinks. Open the Honeywell Total Connect Comfort app and follow the prompts to re-add the device. You will need your 2.4GHz network name and password.
IF THAT DIDN'T WORK Your router may have updated and blocked the device. In your router settings, ensure it's broadcasting a 2.4GHz network (not 5GHz only) and that MAC filtering or a firewall isn't blocking the dehumidifier.
HEADS UP The WiFi module only works on 2.4GHz networks. It will not connect to a 5GHz-only signal. Also, physical distance or thick walls will weaken the signal.