@Steevie This is what you need to do to restore control to the lighting unfortunately. This is a known issue with our newest firmware update but should be a one-time thing. Sorry about the inconvenience, but the update significantly changes the way the software addresses each device and it creates this quirk when upgrading in rare instances.
I posted more about this on Reddit here: https://old.reddit.com/r/Corsair/comments/1caiub4/2_qx_fans_not_getting_detected_in_new_icue_link/l0sd1sv/
You can also read about the Known Issues here: https://www.corsair.com/us/en/explorer/diy-builder/blogs/addressing-over-current-protection-issues-expanding-the-icue-link-system-hub-to-24-devices/
shocksim's post in ICUe Link erkennt Lüfter nicht was marked as the answer