give it time. Also check thread about natural muck cleanup. Get you some bacteria going to speed up the process. While you're waiting for the 'one flush' get some ZEP septic cleaner from Home Depot, or some Enforcer septic tank bags from Walmart. Both are the same, have same bacteria as one flush, but 10% active bacteria per gram,BUT you can get 1 lb for the cost of 1/2 oz of One Flush.
Put in 2 lbs. wait 2 wks then put 2 lbs more and taper off every 2 weeks.