You're missing the bits of atmosphere right under (and inside) your nose.

It's also not like other wavelengths are reflected right back, but when the atmosphere can absorb them, it will also emit them. (Radiation tends to be symmetric like that.) Conversely, the emitting panel will absorb this radiation, until equilibrium is reached.

That means that you need to use wavelengths where the air isn't literally glowing, if you want radiation cooling to work at all.