I cleaned the gear, adjusted the plunger, changed filament, releveled the platform. Nothing worked.
The filament would just "drool" on the nozzle. If I put more pressure, I would get the "click click" sound.
Here's what I found. Enter the "load filament" mode. Cut off the "string" that comes out and measure it. If it's less than .4mm in diameter, there's probably some sort of obstruction in the nozzle.
Get some #30 magnet wire (Radio Shack has it--about .26mm diameter). Cut off a three inch long piece. Go to the menu and "preheat" the extruder. Using pliers, insert the wire into the heated nozzle and pull it out. You may need to do this three or four times (new piece of wire each time).
Enter "load filament." The stream should be solid, not curling and drooling. It should measure .4mm or a little more.
Now, it's building just like new!