I know this thread is over 4 years old, but nobody ever responded to it, it's your only thread, and I saw that you were online. :p
That plug at the top just needed to break the surface tension and drop, so that it could re-mix with the rest of the goo. I'm sure it must have done that by now. :p
Also, if that was the first time you had run it in a long time, you'll probably want to run it for 6-8 hours a day for a couple of weeks until it clears up. Again...you probably discovered all this on your own by now. LOL!
Well there...I tried. :p