Do you have a camelbak? Does it have the switch near the bite valve to turn the flow on and off? It looks like a sprinkler valve. If so, turn it the other way and you should be in business. Also, be sure to remove the plastic packaging from around the bite valve. Also, you will need to bite down on the valve at the end and suck for a few seconds until the water comes through the line. You always have to treat it like a straw, it shouldn't just run on you. If those two things don't fix it, remove the tubing and try to run some water through it to see if you have a blockage somewhere. Then just keep isolating components until you find the problem. Camelbaks are very modular and easy to diagnose.