Common error codes Cowork can return when something goes wrong, with the fix for each.
Before anything else: Run the check
wp-admin → Cowork → Run the check tests every step of the connection from your site’s side and names the one that failed, including whether Claude ever reached your site. Start there; the codes below are what it, or Claude, may show you.
HTTP 401 Unauthorized
Your site refused Claude’s credentials. Remove the connector in Claude and add it again, signing in to your site afresh. If the licence itself is the issue, the Cowork page in wp-admin says so — check My Account → License Keys.
HTTP 403 Forbidden
A security plugin or host firewall blocked the request. Remember that Claude connects from Anthropic’s servers (160.79.104.0/21), not from your computer, so IP-based allow rules must include that range. See the security plugin compatibility articles in this category — start with Wordfence and Cloudflare WAF.
HTTP 404 / rest_no_route
The REST API isn’t reachable. See REST API not available / 404 on /wp-json.
HTTP 429 Too Many Requests
Cloudflare, Sucuri, or a host firewall is rate-limiting you. See Cloudflare WAF compatibility or contact your host’s support.
HTTP 500 Internal Server Error
Server-side error in WordPress. Ask Claude: “Show me my PHP error log for the last 10 minutes.” Most often a plugin or theme PHP fatal. See Common WordPress site issues.
HTTP 502 / 504 Gateway errors
Your host’s reverse proxy can’t reach PHP. Restart PHP-FPM (managed hosts have a button; self-hosted: sudo systemctl restart php8.3-fpm). If it persists, your host has an outage — check their status page.
missing_openai_api_key
Internal to MXchat support chat on wpfc.com, not a customer-side error. If you see this, contact support.
license_not_found
The license key you entered doesn’t exist in our system. Double-check it against My Account → License Keys. Watch for confusion between the letter O and the digit 0 (license keys are all uppercase letters and digits, no lowercase).
rate_limited
Too many requests in a short time. Wait a minute and try again. If it keeps happening, email support.