PCI slot not working on ASUS H97-Plus MB

I have an ASUS H97-Plus Motherboard, intel core i-5 4590 cpu, EVGA GeForce GTX970 Graphics card, and an ASUS Xonar D2 Audio Card. Running Windows 7 64 bit. The ASUS D2 audio card will not work in the PCI 1 slot BUT it WILL work in the PCI 2 slot (slot 2 is closest to the edge of the MB). The D2 card gets quite hot and because it is close to the edge of the MB, I feel it is a bit too much heat so close to critical pin connectors. Does anyone have any ideas as to why PCI slot 2 will work, but PCI slot 1 will not? Yes, these are regular PCI slots (Not express) and yes I know the D2 connection is older tech but the sound is incredible. I'm just looking for any suggestions as to how I get PCI slot 1 to work. Driver for the D2 successfully installed and the card does work - just not in the slot I need it to.

Maybe some option in BIOS to enable/disable?

Tried that - no options in the bios

Thank you so much for the ideas. I will check both the Configuring section AND the IRQ settings.

Turns out the PCI slot is defective. The two PCI slots are "plug-&-play" so there is nothing in the Bios for either one. Apparently, one of the pins in slot 1 is bad. Even though the board is new, ASUS will only repair the slot at MY expense (estimated at over $100.00). So much for ASUS warranty. Can't say their customer service is much better either. Their verbal communication skills leave a lot to be desired. Let's just say that it will be a cold day in hell before I buy anything from ASUS again. A warning to all you folks out there thinking of buying components and trying to build a custom pc. Do NOT buy ASUS components. Be very suspicious of any reviews that give ASUS high marks for quality or for warranty service, and don't trust anything else that reviewer has to say.

Sorry to hear about the warranty issue.

Maybe a piece of hair or something got stuck in there?

Get a flashlight and visually check the pins. Maybe one of them got bent and shorting?

I purchased the board in December, but due to a whole lot of family issues I was not able to begin the build until May. So, my 30 day option to return it has long ago expired. The problem is a bad pin in the slot and ASUS wants as much to repair it as it costs to buy a new board. Crazy, huh? So I am, proverbially, SOL. And yes, the ASUS product warranty policy is not at all user friendly. I suspect that the only way ASUS would ever consider changing their policy is if it begins to hurt them in their pocketbook. Arrogance has a way of coming back on folks who exercise it - kinda like karma. Anyway, I really appreciate everyone's response and ideas. Bottom line? I'm looking into a local shop to see if the bad pin can be fixed at a reasonable price - if not, I might still be able to use the board for a future build where the PCI slot is not needed. Thanks again to all for your input. I really appreciate it and your time.