You’re not providing a lot of information. Since you can connect the remote to Homey, I assume that you’re using the experimental v5 firmware? Do you get any errors? Where exactly does the pairing process fail?
Did you reset the driver by sticking a pin in the reset hole (shown in your photo)?
Which firmware version are you running (in the Homey mobile app, go to “More > Settings > General / Meer > Instellingen > Algemeen” and look at the “Homey version/versie”)? Since you say that “The remote I can connect to Homey”, it should be the experimental v5 firmware because earlier versions of the firmware couldn’t pair with that particular remote.
Ikea’s documentation says to have minimum one light connected to it when pairing.
Not sure if that makes a difference. But at least then you will get a visual confirmation of a reset.
I noticed that I sometimes needed a bit of a longer hold with the pin in the hole.
And the toggle power 6 times should do the trick.