Without further information, based on what you posted, it sounds like this customer is on per-device licensing and someone applied 2 licenses to the same switch, leaving them 1 license short, I've run across this on an AP deployment. I can't recall exactly what the screen looks like, but under device licensing it should show a qty 2 on the switch using both licenses, just edit / remove 1 and it will free it back up and can be applied to the 3rd switch.
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