I once listed >10k worth of equipment on eBay (spring cleaning) and got instantly banned as well. However, in my case I explained all to eBay support and they put me back on. So try again and again until you get to somebody willing to speak to you.

I once had an Amazon seller ban right after enlisting items and it just went into an infinite automated loop which looked like "give us a proof!" "here is the proof" "give us a proof!" etc. Back then I didn't know you had to literally bribe Amazon managers via some "external consultancies" (friends) to reinstate you back. Maybe eBay is doing the same now...