I'm not sure what you've done for troubleshooting, but:
Try plugging the mics into another device and testing it, if you can, just to eliminate a possible cause.
Also try plugging the mics into different ports if you have them. If you had them in the front jack, try the rear instead, etc.
Also, go directly to the ASUS website
and make sure you've updated your sound drivers.
We look forward to a response.