Cannot get 3 x RTX3070 to work with risers

[Rythmicone]

Hello!  I am new to the forum, and newish to mining - so any help is appreciated!
I was mining with 2 3070s in my ga-z170-ud3 gigabyte mobo 7600k Intel - worked fine.  Wanted to add a card, and got some pcie-3.0 risers.  Hooked everything up and it wont even boot.  Things I have done :
- Cards tested, and working
- Power supply is Corsair 750i
- tried 1 card on a riser, 2x8pin powered from PSU, and riser powered with peripheral 6pin to 4 pin molex.  No luck.
- tried powering the riser with other PCI-E from psu, card powered, afterburner doesn't see it.
- Have 12 risers, none work.
- put 2 cards back in rig right in mobo slots - works again.

From what I have gathered, I either need a different riser or my power supply doesn't like it.  Although it should power 1 card on a riser easily, it isn't found by afterburner.  Is there a certain riser I need for the 30xx gen cards?  I have 2 power supplies ordered, RM1000X corsair.  Hopefully that helps.  I am at a loss.  Any help is appreciated!  If I missed some info please ask away!

Thnx!

[tpd09]

try one of the linux OS - HiveOS/RaveOS/Simplemining

Upgrade bios to newest (important in case of problems)
Set boot device to USB/pendrive or HDD/NVME depends of your disk
Enable 4G encode
Set PCI-E support to Auto
Enable onboard graphics (PEG -> IGD)
Plug your monitor into the ONBOARD graphics card
Optionally enable S5 sleep support

boot with one GPU and add one at a time if all goes well

[Rythmicone]

Thnx for the advice!  I ordered an Asus Mining Expert and 2 RM1000x Power supplies. Hopefully this helps too.  I think I burned a PSU or a pciex4 slot on the mobo.