I have a hunch,...just my 'gut' feeling. In coffee enemas, when not much comes out,...it's said to be a clear indicator that we are dehydrated. (The body takes any liquids given it,...and says, "Thank you very much"!)
One of the first flushes I did in 2010 was the same way.
I didn't as much as pass gas. Three days later,...Katie bar the door.
Just a guess my friend. I'd try drinking 1.5 gallons a day for a few,....and try again. (I'll bet you a GREAT flush!) :-)