Oil will typically stay in the stomach for many hours so your issue is pretty normal. Doing a flush with undigested food still in the stomach does not work so well. Better to do it on an empty stomach if you can. It will typically take many flushes to get the GB working the way it's supposed to so patience is key. I had to do 6-7 Liver Flushes before I could feel my GB working right after a meal.
Maybe do some colon cleansing before the next flush as well to make sure the intestines are clear.