Like @Michael is saying: did you actually add all your IKEA devices to the gateway first?
The correct sequence is:
- connect the gateway to your home network
- install the IKEA app on your mobile phone
- add IKEA bulbs/sockets/etc to the gateway using the IKEA app on your mobile phone
- install the IKEA Gateway app on Homey
- configure the IKEA Gateway app so it will connect to the gateway
- add devices in the Homey app (choose “IKEA Tradfri Gateway” > “Group/Light/Plug” > “Install”, and you should be presented with a list of devices of that type that are connected to the gateway)