Go up to the person on the ap and tell them to dissconnect for a min so you can crack the wep. or open up wireshark and see if your packet are being sent.
if you really want to be a jerk (like me) send a mass attack.
aireplay-ng -0 0 -a xx:xx:xx:xx:xx:xx DEVICE xx is ap mac and device is you guessed it, ur device. Then it will knock everyone off at the same time. Remember only test on your own ap!!! or a firends ap like i do.