This guide summarizes the most common sticking points in Claude Opus 4.6: login verification failing, messages not sending, the model being unavailable, and file upload/parsing failures. If you run into issues, avoid repeatedly refreshing—troubleshoot in the order below, and you can usually identify the cause within a few minutes.
Login & verification failures: check your environment and account status first
If Claude Opus 4.6 shows CAPTCHA/verification failures, first check whether your network environment is stable. Try to avoid frequently switching nodes or using blocking scripts. Then confirm your browser hasn’t disabled cookies; if needed, use an incognito/private window to log in to Claude Opus 4.6 again.
If the same account is signing in across multiple devices frequently, Claude Opus 4.6 may trigger risk controls and repeatedly prompt verification. In that case, log out on other devices and keep only one active session. If it still doesn’t work, try switching browser engines (for example, from browser A to browser B) and test again.
Messages won’t send / model unavailable: usually congestion or requests that are too large
If Claude Opus 4.6 shows “model unavailable” or sending fails, the most common causes are server-side congestion or temporary rate limiting. Try splitting a long message into two parts, or reduce the amount of content you paste at once, then resend to Claude Opus 4.6.
If failures continue, refresh the page and re-enter the conversation; sometimes an older chat with a very long context can also slow requests. You can also start a new chat and restate the key background in Claude Opus 4.6 to avoid continuing with an overloaded history.
