Similar thing happened to me back in November 19 shortly after GitHub outage (which sent CC into repeated requests and time outs to GitHub) while beta testing Claude Code Web.
Banned and appeal declined without any real explanation to what happened, other than saying "violation of ToS" which can be basically anything, except there was really nothing to trigger that, other than using their most of the free credits they gave to test CC Web in less than a week. (No third party tools or VPN or anything really) There were many people had similar issues at the same time, reported on Reddit, so it wasn't an isolated case.
Companies and their brand teams work hard to create trust, then an automated false-positive can break that trust in a second.
As their ads say: "Keep thinking. There has never been a better time to have a problem."
I've been thinking since then, what was the problem. But I guess I will "Keep thinking".
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Honestly its kind of horrifying that if "Frontier" LLM usage were to become as required as some people think just to operate as a knowledge worker, someone could basically be cast out of the workforce entirely through being access-banned by a very small group of companies.
Luckily, I happen to think that eventually all of the commercial models are going to have their lunch eaten by locally run "open" LLMs which should avoid this, but I still have some concerns more on the political side than the technical side. (It isn't that hard to imagine some sort of action from the current US government that might throw a protectionist wrench into this outcome).