i had gotten a Corsair Lighting Node Core and 2x SP120 Pro fans and had constant issues with iCue faling to recognize the Node.
after ~3 updates to the software it seemed to be fixed for a while(few months) but then the same thing that is happening with you started appearing with each fan randomly.
one would be auto-recognized at boot and set to it's light profile while the other stayed dark, one would boot into rainbow effects while the other functioned correctly, both would boot up dark. never knew what situation they would be in with each system boot.
but each time i started up iCUE the profile would auto-restart and both fans would be back to their set lighting profiles.
finally the Core malfunctioned and ruined the 2 fans attached. now, even when attached to motherboard aRGB headers they only show a light pink and light patterns do not work.
i believe the Corsair software and hardware is just garbage at this point. many users seem to have better results, but in the process of determining the problem i found many, many threads on help sites and Corsair forums with users having similar problems.
i would contact Corsair and try to get replacement fans, Node, or full set. hopefully you wouldn't need to RMA the whole case.
maybe first try uninstalling/reinstalling iCue and see if that works for now.