Two Port USB Adapter--Only One Port Recognized

I’m using a MayFlash Genesis USB adapter that has two controller ports built in. Windows 10 recognizes the adapter as having two ports. However, RetroArch does not. When I go to to bind input 1, it only shows the adapter on port #0. Port #1 doesn’t show up. The next available port is NA #2. I have a similar MayFlash SNES adapter and that shows up as port #0 and port #1, allowing me to bind player 1 and 2 controls to the same adapter. Is there anything I can do to get RetroArch to see the second port?

Edit: I forgot to mention I’m using RetroArch 1.3.6.