[BUG] Can not LOG IN to web app or CC CLI after upgrade from Max 5x to 20x

Preflight Checklist

• [x] I have searched existing issues and this hasn't been reported yet
• [x] This is a single bug report (please file separate reports for different bugs)
• [x] I am using the latest version of Claude Code

What's Wrong?

Authentication issue where the web app and Claude Code CLI log in both direct me to the log in page but typing in my email account that's associate with my subscription plan is unrecognized. I have exhausted all options including brower cache/ deleting browser stale data, tried log in through every portal (email and Google), etc. The iPhone app continues to work and allows me to log out log back in, Chrome extension continues to work as well. This is a OAuth authentication bug seemingly on Anthropic's server side. I've tried reaching out for support through their proper channels (Fin AI) and have been in a recursive loop getting nowhere. Short of human intervention to properly look at my account and reassign the OAuth backend flow I don't know if this can get resolved. It is a MAJOR bug. Complete lock out of an account in to the most critical surfaces (CLI/ web app) AFTER upgrading to a MORE expensive plan.

What Should Happen?

Anthropic needs to either provide human support or address this critical issue with OAuth log in after plan modifications. I don't know if it is tied to the fact that the plan was created through IOS but it is a major error that prevents log in with a subscribed MAX 20x account email!

Error Messages/Logs

Says "Not Found" after trying to log in on the web app and sends me to "Let’s create your account".

Steps to Reproduce

Upgrade your plan on IOS from Max 5x to Max 20x
Logout of Claude CLI, try Logging back in!

Claude Model

Opus

Is this a regression?

Yes, this worked in a previous version

Last Working Version

_No response_

Claude Code Version

2.1.114 (Claude Code)

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

Terminal.app (macOS)

Additional Information

_No response_