A fan is designed to turn one way, and push a lot of air. If it is turning the wrong way, it puts out a very feeble amount of air.
When your fire is burning, with full feed, you should have 8"-12" of flame above the fire. Unplug the combustion fan for a moment or two, the fire will die down to an idle, only the chimney draft will be pulling air through the fire. Then plug the fan back it, the flames above the fire should resume to be about a foot high.
I'd remove the combustion fan, inspect the fan itself.. a piece of paper, a few pieces of carpet fluff, a quantity of dog or cat hair, anything can clog the inside of a squirrel cage fan, and make it ineffective.
If the fan is clean, then there should be a very strong output from the fan when it is running, like a hair dryer. If not, then the motor may be turning the wrong way, and the fan can't do it's job.. If this is the case, contact the manufacturer for a correctly opperating fan.
Let us know what you find.