I became an obsessive FB marketplace user buying up tons of other peoples old junk until one day I initially offered to purchase a table but discovered that IKEA was selling the same table for 5$ less in new condition. I explained my reasoning to the seller and sent her the link and within minutes I was banned from Marketplace with no recourse. I don't know if she reported me or something.

I was really bummed for weeks because FB support does not exist. But after a while I figured out that if you sign up for FB verified you gain access to human based support. I did so and eventually they managed to restore my account with no reason as to why I was banned. Maybe that will help?