I successfully added some Tradfri LED controllers that we bought with our Pax wardrobes, they have a tiny hole on the flat front that you can put a pin into for 5 secs, then they start flashing and HA Zigbee discovers them 
Good evening, I have the same led controller but always get an error when I turn them on or off from HA “TXStatus.MAC_NO_ACK: 233” does anyone know why, my HA is in the basement and the Tradfri on the top floor, they still go on and off however. any help would be appreciated.