I even tried without the backplate, no luck.
I de-installed the WB, cleaned everything and re-installed it, no luck.
I don't know what to do now ...

I use backplate to i have No issus at All.

Did you use alkohol to remove the old
thermalpadss ?

Thank you for your responses :)
Yes I cleaned everything right.
I re-installed the retail air cooler on one of the cards and the error is still there.
It's like the card is "locked" and triggers an error as soon as the PC starts. The motherboard doesn't boot and shows error B2 (or 62 it's hard tot tell) on a Maximus Apex IX. The white VGA LED is also on.
On my other PC (Asus ROG Strix X570), the error code is 97 and there's also the white VGA LED on...
 

my pc wont boot if the gpu is well screwed on the case, i need to make it sag so it make contact with the pcie slot connector

wow that sucks. keep us updated

Had the same issue with mine after installing my EKWB block on a 3090 FTW. Post code 97, white light wouldn't post. Waiting for RMA now.

I had a similar problem with a 2080Ti and EK Waterbock. Turned out it was the Nickel backplate causing it to not post. I figured it out when I took off the back plate an tried it and it posted. I put it back on and I didn't post again.  After racking my brain for a while over it. I tried loosening the screws on the backplate and poof it posted. You have to be careful of how tight you screw in the back plate on the EK blocks and be very mindful of the placement of thermal pads on it. Hopefully you get it fixed....

Be careful to believe the 1mm pads are enough.
After install please check again your work by open it again and check every pad if you can see the contact!
 
I installed the block 3 times. And have to change the pads into 1,5mm pads in some areas!
 
Here you can see my entry. It musst not be a ekwb thing. -> https://forums.evga.com/FindPost/3218411
Please check that nvidia is allowing more bending. -> https://www.igorslab.de/e...o-heavy-investigative/
Mayby some vrm or memory wasn't on contact to the cooler.
 
Markus

I have EK backplate om my 3090FTW3 Ultra and All is good but i put 2 extra thermalpads on 😎😎

I'm getting ready to install the WB on my FTW3 today and reading this post made me nervous. Did you hear back from EVGA on the RMA?