I have a Predator Orion 900 with a i9 and a Geforce RTX 2080 Ti card- I changed now with two EVGA RTX 2080 Ti FTW3 Ultra Gaming (11G-P4-2487) and a EVGA NVLink Bridge- the SLI is not working and not possible to change in the nividia systemcontroll.
I installed just one, then the other and at least both together; this to check if both cards are ok, the SLI bridge I can change the LED in the X1 EVGA program.
I re-installed all geforce drivers/programs- no way- I made a clean new installation of windows 10- no way.
GPU Z shows SLI as disabled, HWINFO64 as not present...
 
Maybe there is an idea for a solution.
 
No question; I would be more than happy 

NVIDIA SLI requires that cards/slots be running in at least x8 Mode..Your GPU Z 1.PNG shows that card/slot as running in x4 Mode.

You need to check how the PCIe slots on your motherboard work..Maybe another add-in card (sound card, whatever) is putting that one slot into x4 Mode which does not support SLI.
 
Run the "Render Test" in GPU-Z and see if it bangs up to x8 or x16 Mode.

Which i9 do you have and what motherboard is in it ?  If its like the i9-9900K or 10900K there won't be enough PCIe lanes on the cpu either to run at X16 3.0-X16 3.0

Thank you so much Bob.....!
Not even the Acer support checked this and I checkd it when I run GPUZ but didn't know if this is the "killer"...
I made the check and still in 4x- 
 

It is the i9 - 9980 XE, the MB is from Acer, based on intel x 299- the power unit has 1000w
Acer have models with 2 gf rtx 2080 ti, but my EVGA is much bigger and needs 3 slots.
 

Like I said, you need to check how the PCIe slots on your motherboard work..That info should be in the manual, but then again, we're talking Acer here..Maybe another add-in card (sound card, whatever) is putting that one slot into x4 Mode which does not support SLI.
 
If you have any other add-in cards installed..You could take them out for now.

Yeah that setup is more then capable of running PCIe 3.0 x16 on both cards then.  it doesn't matter if another slot is populated. If its an X299 board with 9980XE it has all the pcie lanes needed for running the full SLI, if the nvlink bridge is connected and the top card is in the top slot then the cards have to be in the right slots.  With both cards installed, and the nvlink installed uninstall your drivers with DDU in safe mode, in the DDU setting check the box to not let windows install the drivers.  Then use the option uninstall but do not reboot and once the drivers are uninstalled reinstall the drivers you have downloaded then reboot. 

Details of the mb and PCIe slots I will ask Acer and will see if it works for sli or not.
I did not installed any other cards- the two EVGA's needs 6 slot's and not anymore space for other cards.
Question will be, can I bring this slot on x8 or x16 Mode
 
But tanks you so much Bob for your helping hand and feedback!!! 
 

No problemo..But yeah, the whole issue is that one slot/card running in x4 Mode for whatever reason..That's a no-go for NVIDIA SLI..Slots/cards have to be in x8 or x16 Mode.

peteruswiss
Details of the mb and PCIe slots I will ask Acer and will see if it works for sli or not.
I did not installed any other cards- the two EVGA's needs 6 slot's and not anymore space for other cards.
Question will be, can I bring this slot on x8 or x16 Mode
 
But tanks you so much Bob for your helping hand and feedback!!! 
 

All X299 boards work with SLI 3.0 X16 , i would just take the side panel off and read the model number right off of the motherboard. I assume if you were not having the issue before the bottom card slot is where the issue is. Did you install both cards individually to make sure they would run at X16 3.0 on the top slot?  Is the second card you added Brand new or used ?