Air Brakes wont grab when i apply them on my trailer what should i do?

Get the trailer in for repair, immediately. Not only will the DOT crucify you if you catch you running around like that, but there's also the safety concern. One of these trucks loaded still requires the length of two football fields or more to come to a complete stop at highway speeds - and that's with a properly operating set of brakes.

If it's a company truck, get on the Qualcomm, get on your cell phone - do whatever you need to do to contact your dispatcher right away. If they blow you off, then make sure your log books are in order, stop at the next scale house, and request they Level 3 your vehicle - the company will be forced to take action at that point.