DIAGNOSIS This is a classic 2.4 GHz WiFi setup hurdle. The Midea Cube, like most smart appliances, only works on a 2.4 GHz network, and your phone might be trying to use 5 GHz or a mesh network that's causing confusion.
FIX Here's the process that usually cracks it. 1) On your phone, go to WiFi settings and temporarily turn OFF any "Smart Switch" or "Auto-join" feature that jumps between 5G and 2.4G. Better yet, if you can, go into your router settings and give your 2.4 GHz network a different name than your 5 GHz one. 2) Connect your phone to that 2.4 GHz network. 3) Put the dehumidifier into pairing mode (hold the WiFi button on the unit for 3 seconds until the light blinks). 4) Now try the app setup again, making sure you're entering the 2.4 GHz network password correctly.
IF THAT DIDN'T WORK Try a factory reset on the dehumidifier's WiFi. Unplug the unit, then hold down the WiFi button on the control panel. While holding it, plug the power back in and keep holding for another 5 seconds. The WiFi light should flash rapidly. Now try the setup process from scratch.
HEADS UP If your router uses a "mesh" system like Google Nest or Eero, you might need to temporarily disable the 5 GHz band entirely in the router app during setup. It's a pain, but it works.