One of my breast does not produce much milk. When I pump probably get 1.5 oz at the most whereas the other one is I get a solid 3-4 oz.

I keep trying to have the baby latch on the unproductive one to increase milk supply, but he gets so frustrated because nothing comes out. I've been increasing my pump time on the unproductive one but still no increases. Any helpful advice to increase one breast that has a low milk supply?