08 Audi A4 with TPMS icon issue.
 

I've searched a few times, but haven't been able to find a successful answer. The "low pressure" warning has come on in the display area of our dash. (cross section of a tire icon with an exclamation mark inside it). I aired up all tires to 37 lbs and even added pressure to the spare tire, just in case. Still have the light.
The A4 has the Audi MMI (has the little flip board to add SD cards or remove the Nav DVD). I've tried depressing the "car" button, but it only gives me one option that only displays unchangeable information. If I try the "settings" button, I get changeable info such as language, or distance settings. THere is a "delete user" option and an option to set the system back to the "system default" setting.
Any insight to resetting this would be appreciated. (Unfortunately this car came sans a manual!)
Thanks in advance!

richy