Shook and shook! The only time I've ever had a nitrate reading was while cycling so I know it works
You need to shake the #2 solution a lot BEFORE
adding the drops to your test vial. Then shake for a minute after adding.
Originally I just barely shook the solution bottles before adding the drops and then I shook the vial for a minute and got zero readings. But once I started shaking Bottle #2 for the required 30 or 45 seconds first, I noticed that I would start seeing readings starting around 40 seconds into the 1 minute shaking of the vial.