I have the same problem. My Asus Prime Pro x470 appears in iCue but the lights just freeze when the plugin is active. Whats weird is my Asus tuf 3070 is working and that is also going through Aura.
I have reinstalled Armoury Crate a few times, restarted, disabled all Asus services, but the motherboard lights will just not do anything. I can get the 3070 to work with Aura or iCue, just not the MB.
I am using Plug-in v. 1.2.1.0.
I can't think of anything else to try.
edit:
I just tried the .dll from this thread https://forum.corsair.com/v3/showthread.php?t=192965 and it worked.
I disabled the plugin in iCue and replaced the .dll in C:\Program Files (x86)\Corsair\CORSAIR iCUE Software\plugins\ASUS with the one from Asus Plugin.zip. I also renamed the zip .dll from asus_motherboard_plugin.dll to asus_plugin.dll, I don't know if that was necessary. Then renabled the plugin in iCue. The version from the zip file is 1.0.4.0
Of course the my GPU no longer shows up, but I just proved (to myself) that something is wrong with plug-in 1.2.1.0 and my MB.
Also I stopped all Asus services and figured out that the Asus Com Service is the only one iCue needs to control the MB. Armoury Crate will not start properly without its service running, but I don't use that software anyway.