Yes. I don't enjoy talking about it because it is upsetting to me. But they felt the game contained sexual content depicting minors. They did not elaborate on where or how. I can only assume they were able to use the character create to make a character that looked inappropriately young, or the random generated characters I had in an early build did so by bad luck.
I have since added additional character create rules to reduce this possibility (breasts required unless masculinity is raised). I can't go into detail about Steam's rules, but the decision is final.
Have you possibly thought about advertising it through FA or E621 (or other similar places)? With links redirecting to this page and other places.
It still comes up through google and I can still load this page from other devices I am not logged into. So I feel like there may be other opportunities.
Also GOG has nsfw games on their website/browser now, so that could be another place to try selling it.