Ikea devices are notorious for not wanting to pair to controllers running on any other channels besides 11, 15, 22 or 25. These channels are typically used for ZLL (Zigbee Light Link) and it’s where Ikea devices perform best. Also, they are notorious for not fully resetting. When I have to re-pair my Ikea devices, I typically reset them three times (6 on/off cycles for lights and 4 seconds holding reset for remotes) before ever attempting to pair them plus I move them right next to the controller. So, check which channel you have your controller set to and if it isn’t one of the 4 listed above, I’d try changing your Zigbee channel. It’s a MASSIVE PAIN IN THE A$$, but it might work.
The other piece of advice I have is that if you have a Hue hub, try adding them to that and then using the Hue integration to get them into HA. The reason being is that most Ikea devices are ZLL profile devices that downgrade to ZHA when attached to a ZHA controller. This will cause problems eventually (devices dropping, improper routing, etc). I’m not 100% sure, but I think the CC2531 handles both ZLL and ZHA equally, so you might be OK there.