brand new Mac air battery not charging

Be sure to follow the steps in If your Mac battery won't charge - Apple Support.

If you have reason to believe the battery is not charging, then proceed with "Get your Mac serviced."

Be sure to use the power adapter and charging cable that came with your Mac before concluding something is wrong with the Mac.

Get it to Apple and have it evaluated. Apple batteries are very good, but they still requires a minimum amount of user care. Leaving it at 0% power for an extended period of time is not good.