No, we didn't. Had no clue about any exceptions at all.

This seems to be common-case for most people who were fined but claim that they were not able to afford healthcare.

Unfortunately, and I'm going to be very frank with you, this predicament is simply that you weren't proactive about researching your situation and so you accepted the fine without much thought or effort.

The information was and still is widely and immediately available upon even very basic attempts of research. It was also presented to you when ACA first rolled around. It was also not in 'fine-print', but plainly stated and in clear view. It was also a big talking point behind ACA, since quite a number of US Citizens cannot afford healthcare and so shouldn't have to be fined for something that they can't afford (and thus aren't fined). They made it as clear as they possibly could from the very beginning and even now as we enter 2019 where these things have changed, you can still readily and easily find information for 2018 and prior.

You have to be proactive about your life, friend. Never expect the system to work in your favor for no reason beyond that it should.