COAT, EXPOSE AND PROCESS BEFORE IT DRIES OUT
The plate had dried before it could be processed and lost sensitivity

The collodion wet plate required that the photographer dissolve a nitrated cotton into a mixture of alcohol and ether, plus soluble iodide. This thick liquid had to be poured onto a spotless, clean glass plate, then the excess drained off. The Alcohol and ether were allowed to evaporate. The thin film remaining was then sensitized (in the dark) by immersion in a solution of silver nitrate. A light-sensitive silver iodide was then formed. While still damp the plate had to be exposed immediately. It also had to be developed by pouring on developing agent (sometimes pyrogollic acid) before the surface dried. If the plate dried prematurely, you obtained the effect shown above, where sensitivity was lost. There was no temperature control, the developing solution yielded an image almost instantly.
The plate was then fixed, washed, carefully dried, and then coated with a top lacquer, as the emulsion was very fragile. Doing this under wartime conditions with limited fresh water, the hot sun beating on the dark light-tight wagon was an amazing accomplishment.

The Ansco advertising photographers, McKinley and Bengston, actually made and exposed wet plates to show how it was done, using cameras and lenses of the era.