The real story was that last time there was a shortage, he did ramp up production. But after the shortage ended, his customers dried up immediately and he was left with paying unemployment for all the new workers that he had to fire now. It nearly destroyed his business, and he's not making the same mistake again.
His masks cost 10c where Chinese-made masks cost 2c. There's no way to get hospitals to keep him in business during non-crisis times at 5x the price. If there were, he'd do it.
So it isn't just inability to physically increase production. Economics factors in heavily, too. If he could charge more for these masks, he could bank that extra and pay the unemployment (and other business expenses from ramping down) after this crisis ends.