DIAGNOSIS Solid yellow on the status light means it's powered on but not connected to your Wi-Fi. This is almost always a Wi-Fi credential handshake failure, often after you changed your router or password.
FIX You need to force it into setup mode. Unplug the hub. Hold down the tiny reset button on the side with a paperclip while you plug it back in. Keep holding for about 10 seconds until the light starts flashing blue and yellow. That means it's broadcasting its own setup network. Go to your phone's Wi-Fi settings, connect to the network named "MYQ-XXX". Then open the myQ app—it should automatically prompt you to set it up on your home network again.
IF THAT DIDN'T WORK The hub is notoriously picky with certain dual-band routers. If it keeps failing, try temporarily disabling the 5GHz band on your router during setup, so it only sees the 2.4GHz network. Set it up, then you can turn 5GHz back on.
HEADS UP The hub cannot connect to Wi-Fi networks that require a secondary login page (like hotels or some apartments). It needs a standard home network.