You clogged it. I bet not all the coconut floated, or something along those lines....i've clogged tubes with VERY little hop matter before.
My advice. First, clean out the outtube. Get out a bottle of starsan. Vent the keg, and leave the pressure relief valve OPEN so beer doesn't come out of the diptube. Remove the post, (spraying everything liberally with starsan, and clean it out. Pull the diptube and clean it out if you want, but usually it's the poppet in the post that clogs. Starsan everything more and reassemble and check.
If this doesn't work, I've had material clog the quick disconnect poppet as well, (it makes it past the post poppet, and clogs the QD). Take this apart as well and clean it.
If your line then clogs up again, you have to get really radical. Sanitize your arm, pull the diptube almost all the way up, and put something to filter the beer over the end of the diptube. I prefer a 1 gal paint strainer, (sanitized in starsan), with a ziptie (starsanned), ziptied over the end of the diptube.
Just be really careful with tons and tons of starsan, and you should be fine. Remember to re-purge the keg whenever you reassemble it so you don't have oxygenation problems.