I had this problem, too. Was able to figure a few things out. Here's my story.
Got my Ironclaw a few days ago, used it with the WiFi dongle on WiFi mode, when today, I finally decided to go into iCUE and look through settings. Noticed there were firmware updates, proceeded to update the Dongle/WiFi Receiver firmware from v1.x to v5.x... it went through then said it had failed. D'oh! Retry button didn't do anything. Reboots, experimentations, etc. nothing was working. The only response I could get from the mouse or iCUE with regard to the mouse was if I plugged the USB cable in, and I would see a small icon for the mouse-and-cable appear in iCUE, then it would go away, and sometimes the mouse would actually move the cursor, but verrrry intermittently, and jittery, and within 30-60 secs, fail to work at all. The WiFi receiver entry in iCUE would never light up the "Pair" button.
One important thing that had confused me at first is that I was thinking of the WiFi "pair" process as identical in the method of pairing you use for "Bluetooth Pairing" -- it is not. For the Pairing process with the WiFi receiver, you must have the mouse plugged in with the USB cable AND the WIFi receiver also plugged in! Then, the button lights up, and you can pair the devices, and finally unplug the USB cable and use it with WiFi mode!
I'm not sure if it made a difference for the pairing process I just mentioned, but I had to flip over to Bluetooth mode to actually use the mouse in order to get its firmware updated, and pair it with the WiFi. Note: While in Bluetooth mode, though, the mouse does not show up in iCUE. Hence, preference to switching back over to WiFi.
So, not promising they'll work for everyone, but here's the steps I took:
Unplug mouse, and WiFi receiver, turn mouse to Off mode.
Hold down the "Profile Button" (the button between the scroll wheel and the lower middle button), and flip the mode switch to Bluetooth
Pair over Bluetooth with the PC.
At this point, the mouse was now working for me.
Since I am going to update the firmware, plug the mouse directly in with USB (continued to work fine while also on Bluetooth)
Go to iCUE and I see the mouse, finally!
Go to the Mouse entry, click Device Settings, choose "Check for Updates". Then update the mouse firmware. NOTE: It will probably tell you to plug in the receiver, but it's okay -- just click "Skip", we just want to update the mouse firmware right now.
With the firmware of both the WiFi receiver AND mouse updated, I felt better. Things should work more smoothly, now.
Now, plug the WiFi receiver back in.
It will show up in iCUE, go to its entry.
With the mouse still plugged in, and the WiFi receiver plugged in, you should see the "Pair" button light up.
Click "Pair" and follow instructions. You should get the success message.
Now, flip the mode switch on the mouse to "Off", and disconnect its USB cable.
Flip the mode switch to WiFi.
It's now working!
Dance, cheer, curse, or do whatever it is when you feel accomplished.
Hope this helps some folks coming here with this issue!
-==SteeleMage==-
