Denoise 2 can't learn noise in Premiere Pro

[landhofilms]

Thanks in advance for the help. Denoise 2 seems to work like most other similar effects. I've read the instructions for how to capture background noise. I have a nice 2-second section of my clip of pure background noise with no dialog. It seems to be capturing when I press "learn" and play that section, but when I play the clip, both with "dynamic profile" on and off, there's no effect, and when I solo the noise, there's nothing there.

Adaptive generally works well, but in this clip, it ramps in too slow off the top.

Any ideas?
Thanks,
Dave