Z97E-ITX/AC Bifurcation

Hello, I have a Z97E-ITX/AC mobo, bios version P2.20. I upgraded the unit from Win7 Home to Win10 Enterprise edition (clean install). My problem is that the PC no longer displays the PCIE slot X16, primary GPU (GeForce GT 740 2gb) in the device manager. There was already a (1 x 2 riser card) installed in the unit so I'm thinking I may need to update the bios to a version that enables PCIE bifurcation. This is just my assumption. Can someone tell me which bios version I'll need for this or is there something else going on that causing my problem.. Thank you so much

Good morning, I also updated the bios to the latest version P2.20. After the initial Win 10 install the card was detected but after running the first Windows Update > (View optional updates) the X16 slot was no longer there/ detected. The unit has an i7 3.2 GHz processor and PCIe 3.0 interface on board.. Thank you