So like many of you I had the Red Triangle issue.
I previously bought the h100i Elite Capellix AIO but a couple of months ago purchased the LED upgrade screen. For the first few weeks everything was fine, I then decided to add a usb-c connection to the top of my case, shortly after this I started getting the RTOD, at first I thought I had disturbed something but the way all my cables are routed in my case it was hard to see how this was possible, none the less I checked all the cables to the Commander Core were in correctly and pushed in nice and tightly, started thinking was it a power draw issue but ruled that out by disconnecting the previously installed usb-c cable.
I was still having issues and then read on here that doing a power cycle worked as it reactivated the firmware, this actually worked at first for me but the RTOD started showing again and as before the LCD screen did not show in iCUE, it then got to the point that the power cycle trick was not working.
One day after booting up the screen kicked in, I looked in iCUE, the screen was not showing still but I noticed there was an firmware update to the Commander Core, so I updated and rebooted the PC, the RTOD came back.
I then decided to double check all the cables again, pulled the pump cable out from the top of Commander core and made sure I pushed it back in securely, I also done a full power cycle.
After rebooting the PC the screen was working and showing in iCUE, I took this opportunity to download the beta firmware linked on here and update the screen, since then my screen has been totally fine (touch wood), a little frustrating that I can't quite pinpoint what has made it start working again, I was literally about to put the old led housing back on the top of the pump but whatever I have done seems to have got it working again, been OK for a week now.