I connected a Deco X20 via ethernet to the modem/router combobox with Dynamic IP, AP mode, and everything seems to work fine on the main unit.

Then I added another Deco X20 on 1st floor. It looks okay with a stable green.

However, none of my devices is able to connect to the 2nd unit, even if my device is right next to it. When I used the Deco app to force assign a device to the 2nd unit, the device simply disconnects from the network. I tried assigning my iPhone and PS5 to the 2nd Deco unit, and both simply disconnects. I've swapped the Deco units, still doesn't work.

Any advice?