I agree about the API Kit. It is difficult to discern (at least in my case) the difference for 0 and .25. I usually put 0, but sometimes it looks like .25.
Recently had it tested at LFS and they indicated .1, so I am comfortable it is good enough since there is no change and I do routine maintenance and test regularly with no oddball measurements.
But OP hasn't advised if using API kit...
I think if cycled and you indicating you have plants, if you have no readings then likely your plants are using up your nitrates.... mine maintain a low level at 5 ppm, and was advised to raise that by this community. I have begun to dose with Seachem Nitrogen, and after first dosing had 10 ppm. It is due for another test today.
54 Gallon Corner Aqueon in it's infancy