It happens.

You just have to disconnect where the line runs to the sprayer nozzel/raindome/ect and let the pump run (with water in the reservoir) for a couple seconds, until water is coming out of the line, then turn off the pump, hook it back to your nozzle/dome/ect and plug the pump back in. It should work just fine, just needs to be primed.
REMEMBER to push down on the collet lock to release the tubing or you will ruin your collet. It kinda reminds me of the finger trap toys we'd get as kids. You have to push down on it as you're pulling it out, or it pulls tight until you break it.