When I go to capture a noiseprint, I don't get a noiseprint or the noiseprint appears around -120 dB as a flat line.
Add Event FX (not Track FX) plugin Noise Reduction by clicking on the "fx" symbol and selecting Noise Reduction.
Select a region of noise in the audio.
Select "Capture noiseprint" in the effects window.
Press play in the Preview window.
Optionally, save the captured noiseprint as a preset.