It is most likely clogged in the section that has a dip in it to make a water trap. Blow at the very end where it drains to the floor. Put you hand around the pipe and blowgun to make a seal. If that don't work, plug the furnace drain with a wet rag or cork and blow again. If that still doesn't work, take a hack saw and cut where a straight section is and use a snake or something to unclog it. Don't cut it in a place where all the water will drain into your motor and electronics. You can get a coupler at Home Depot to put it back together. I wouldn't glue it together in case you need to unplug it again. You don't need to pay an $80 service fee to fix this. You can replace and re-plumb the whole thing yourself for around $10.