For me you are already the hero Bob- I spend two night's for this story...and I was closed to take my guns...
I will check the modell nr, but it is one of Acer based on the intzel x 299.
between the PCIe slots are two m2 slots and I installed two ssd- don's know if this could be a reason...
 
I installed both cards as single and they worked perfectly before I installed both for sli..or the try for sli...

Go to this page here and see if you can get more details of your specs with the SN    https://www.acer.com/ac/en/MY/content/support 

Let's just hope SLI is even possible in the PCIe slots you need to put those 2.75 slot width cards in..Would be major suckage if not.

peteruswiss
For me you are already the hero Bob- I spend two night's for this story...and I was closed to take my guns...
I will check the modell nr, but it is one of Acer based on the intzel x 299.
between the PCIe slots are two m2 slots and I installed two ssd- don's know if this could be a reason...
 
I installed both cards as single and they worked perfectly before I installed both for sli..or the try for sli...

Most if not all of the X299 boards are made so the m.2 slots will not effect the 2 pcie slots used for SLI, they will affect the lower slots though.  That being said though if the motherboard is an acer model as well its hard to say how they have configured it. 

Yes Bob, I hope too...!
Tomorrow I will bring the Acer support on speed for settle this - I keep you posted  

Thank you for your information, I just found a pic of the mb on the acer community side...and marked thet the PCIe slots are x16 ! .the specs they have to let me know from customer support side....

Yeah so your video cards should be in the top slot and the 3rd slot if your cards are taking up 3 slots each, but it says that the computer comes with its own SLI bridge as well, is the spacing on that one the same as the EVGA nvlink your using, if so then you know your in the right slots. We really need to know if one of those M.2 slots is taking lanes from the bottom PCIe slot. 

If you're not aware of it, slots can physically be PCIe x16 slots but electrically run in a slower mode like x8 mode or x4 mode depending on the motherboard/slot operation..That's what I was talking about before.

bob16314
If you're not aware of it, slots can physically be PCIe x16 slots but electrically run in a slower mode like x8 mode or x4 mode depending on the motherboard/slot operation..That's what I was talking about before.

Yeah i know Bob, i agree but usually they don't let the M.2 slots interfere with the 2 slots needed for full speed SLI. That image is kind of a strange looking critter though. 

peteruswiss 
I installed both cards as single and they worked perfectly before I installed both for sli..or the try for sli...

Both ran at x16 3.0 when running them individually in the top pci-e slot?