Quickly wanted to let this thread know that I was able to connect the Deco and Daikin devices. I know there was an update available for Daikin, maybe that helped

  @JasperNL 

Hi,

I just got mine working as well but I had to change some settings via the web browser.

1st I disabled the 5G(I did this for fault finding you may not need to).

Then I had to set the 2.4G to WPA/WPA2 and AES(see screenshot).

Hit the WPS button on both.

The network status message on the Daikin changed from disconnected for my other network to disconnected from this network.

Rebooted the Daiking and the connection came up.

Then re-enabled the 5G.