I feel your pain, that would be so frustrating! It sounds as if you have been unfairly targeted.
I don't know that you will get anywhere with ebay, I have read of other people in similar positions, banned from selling. From what i recall, very rarely were they able to get it reversed. I've only read of one case. There may be others, of course, that I have never heard about.
You're asking about what legal services you should use to follow up. If I were you, I'd have a good look at past sales and profits to see if it is actually worth it as legal services can be massively expensive & you'd be up against ebay, which has deeper pockets.
I have also heard of other people who were banned from selling and who got around it by opening a new account, on a different computer or device not at their home. But they would have had to have accounts that didn't link to the same address & I presume not the same bank accounts etc.
If you tried doing this at home, the IP would just show up. It is all a lot of bother, unless you happened to be changing houses at the time of the ban.
I think your best bet is to look at the categories on Facebook marketplace and try there.
Or if you have a specific range of items, see if there is a facebook interest group for them where you could sell to the converted.
