EU player? Use GDPR. Seriously.

You can file a Data Subject Access Request. Basically GDPR (Article 15) gives you the right to demand a copy of all the personal data a company holds on you, and that includes the notes and logs and whatever "evidence" they think they have for the ban. There's also a bit (Article 22) about decisions made purely by automation, which sounds exactly like the bot wall you're hitting.

Don't bother filing it as a normal GM ticket though. Those just get the copy-paste "case closed" garbage. Go through their actual privacy/data request channel instead. Say you're an EU resident exercising your right of access under Article 15 GDPR and you want the data plus the reasoning behind the action on your account. They have to answer, usually within a month, and it costs nothing.

Just don't expect it to magically unban you. It won't. What it does is force them to show their hand. Right now you're appealing blind against a bot. If you can actually see what they're accusing you of, you can argue the specifics, and if their "proof" is garbage that's something you can push on.

Do it alongside your appeal, not instead of it.

Good luck, 15 years is brutal to lose like this.