"won't go on a crank" is shaky ground for assuming the threads are damaged. I'm having trouble imagining what kind of damage could keep it from threading in, but is not visible to the eye. Or maybe you can see damage? That wasn't clear to me from your description. Well-focused close-up pics sometimes show things you can't see by eye. Please supply photos if you are able.

Have you tried it on more than one crank? Any chance your crank is French-threaded?

Besides the nominal thread size, there is also a "class of fit", basically how much smaller the actual dimension is than the nominal dimension. Cheaper pedals generally are made with a smaller thread, to fit easily into cranks whose threads may not be made to tight tolerances. Campy pedals are made with a tighter fit and can be difficult to thread in, even when the crank thread is high quality, such as with Campy cranks.

Repairing the thread is going to be difficult due to the thick hard chrome plating. A machinist can do it, but it requires taking the spindle out of the pedal, and will probably cost more than a pedal is worth. But don't even think about repairing it until you determine what the problem is.

Mark B