If you are doing a fishless cycle and your nitrate is zero, you aren't finished cycling. At the end of a fishless cycle, the nitrate should be off the chart high, well over 100ppm. The bacteria in a bottle products are useless.
Are you adding ammonia (or something to produce ammonia like fish flakes) to the tank to do your fishless cycle? If not, then you're just pumping water as there has to be a food source for the bacteria to form. I know you said in another post that you didn't trust the Add & Wait method but regardless of what type fishless cycle you do, you MUST have an ammonia source. Without it, there is no food for the bacteria so they never develop.