Claude Troubleshooting Guide: Login Loops, Attachment Failures, and Truncated Replies

When using Claude for writing or handling files, the most annoying part isn’t not knowing how to use it—it’s when errors suddenly pop up, it gets stuck, or the output is incomplete. Below is a Claude troubleshooting guide organized by the most common scenarios. From login and network to attachments and rate limits, it helps you pinpoint the problem step by step down to actionable checks. You don’t need to reinstall your system—usually you can recover in just a few minutes.

Login issues: repeated redirects, verification failures, blank pages

If you run into a Claude login loop or a blank page, start with “minimum-variable” troubleshooting: first try an incognito/private window in another browser, then disable extensions like ad blockers and script managers. Many Claude issues are actually caused by cache or extensions blocking the login callback; clearing site data and logging in again often fixes it immediately.

If Claude keeps saying verification failed, check whether your system time is correct and whether your network is using an unstable proxy node; clock drift and node jitter can cause session validation to fail repeatedly. If it still doesn’t work, sign out of all device sessions first and then log in again to avoid conflicts with old sessions.

Message send failures: endless spinning or “Something went wrong”

If Claude doesn’t respond after you send a message, first copy your input locally, then refresh the page and retry to avoid losing your draft. Next, do a key troubleshooting step: shorten each input by splitting long content into two or three parts, especially when it contains lots of code blocks or very long quotes, which are more likely to trigger processing failures.

If the error happens frequently in a specific network environment, try a mobile hotspot or switch DNS and try again; Claude is more sensitive to connection stability, and packet loss can show up as endless loading or submission failures. If it fails repeatedly, don’t spam the Send button—waiting ten-plus seconds between attempts can reduce queueing and retry storms.

Attachments and images: upload failures or content can’t be parsed

If Claude attachment uploads fail, the most common reasons are that the file is too large, the format is non-standard, or the filename contains special characters. When troubleshooting, first convert the file to a common format (such as PDF, PNG/JPG, or TXT) and re-upload with a shorter English filename; for scanned PDFs, it’s recommended to run OCR first or convert them into copyable text.

If Claude can upload the file but “can’t extract the key points,” it’s usually because the content is too dense or there’s too much page noise. You can first crop to the key pages and keep only the tables/paragraphs you need analyzed, then have Claude process them—the success rate will be noticeably higher.

Rate limits and permissions: how to handle 429/401/403 and similar messages

If you see a 429 message, it generally means requests are too frequent or you triggered rate limiting within a short time; the correct troubleshooting approach is to slow down, combine multiple rounds of questions into a single prompt, or wait a few minutes before continuing. If it’s 401, it’s usually because your login state is invalid or the token has expired—just log in again/regenerate credentials.

If you see 403, don’t rush to conclude you’ve been “banned”—more often it’s because your network environment, corporate network policies, or permission configuration is denying access. Testing on a different network can quickly distinguish whether it’s an account issue or an environment issue; if it only fails on a specific company network, asking IT to allowlist the relevant domains is usually more effective.