Ipad air plug in will not charge. turn off the ipad and plug in ipad turns on but doesn't charge?

Bad charging cord/plug

Plug it in to the AC outlet via a charger.
Wait for an extended period of time...then try to turn it On.

Does your iPad turn on ?
If so, what is the battery level shown by the battery icon at the top of the screen ? Does it have a lightning bolt in the middle, showing that it is charging ?

if nothing happens, your iPad battery may be dead.
Take your iPad to an Apple astore to have it replaced.

Try putting it into DFU mode which is
-hold sleep/wake and home button untill it turns off
-let go of sleep/wake button still hold home button for about 10 seconds
-plug it up to iitunes
-and it should be there

Incorrect port part, Wrong polarity for wires connected to the port or poor connection of wires to the port.

When you plug the cord into the iPad do you get a charging icon?

Turn it off when its off connect the cable that's used to charge it to a pc or laptop making sure ipad is still off hold the home button do not let go now keep it held down until you connect the cable and see a picture symbol showing to connect to iTunes as soon as you see that on the ipad you can let go off the home button if iTunes doesn,t open itself you do it it should now see an ipad in recovery mode click on restore or restore and update please note that this will erase your whole ipad back to factory settings

There is only one way I know but you will lose everything up until the last time you backed it up ok turn it off after its off connect the cable to pc or laptop first make sure ipad still of ok then press and hold the home button don,t let go now plug in charge cable keep holding home button until you get the connect to iTunes symbol on the ipad if iTunes doesn,t open then click on it you should now see iTunes has detected it in recovery mode just click on restore or restore and update

Plug it in to a wall charger for ten minutes and try to turn it on. Maybe the ipad doesn't charge with comouter. Or reboot it by pressing home button with top right button on ioad and hold until responds. That can take a minute.

if defective should be under warranty look into replacement / return --

There are many things you might be doing wrong but slow battery charge is a problem with the new iPad. The battery is actually a lot bigger than the iPad 2 which means it is going to take you much longer to charge.
Use the provided charger and don't charge from your computer. It is almost twice as slow to do it plugged into a computer. Charge it at night to give it the most time to charge as possible. I usually turn it off so programs don't run and slow down the charging speed. Every little bit helps.
I can help you with other things too if you ask.