n8n Not Working? Common Errors & Fixes

The 404 'webhook is not registered' error almost always means you're calling the test URL when no test is listening, or the production URL while the workflow isn't active/published. Use the /webhook/ production URL and activate the workflow.

On self-hosted n8n, webhook and OAuth URLs show http://localhost:5678 when n8n doesn't know its public address. Set WEBHOOK_URL (and N8N_HOST/N8N_PROTOCOL) to your public domain and restart.

n8n crashes with 'Execution stopped at this node (n8n may have run out of memory)' when a workflow loads too much data at once. Process items in batches, move heavy work into sub-workflows, and on self-hosted instances raise the Node.js heap limit.

'Connection lost' in the n8n editor usually means the browser's push connection (WebSocket) is blocked by a reverse proxy or rejected for an origin mismatch. Add WebSocket upgrade headers to your proxy and set the public URL and proxy hop variables.

Executions stuck in 'Queued / Starting soon' mean no worker is picking them up. On self-hosted setups, fix mismatched queue-mode settings or restart workers; on n8n Cloud, restart the workspace or contact support.

Google rejects the connection when the redirect URI n8n sends doesn't exactly match the one in your Google Cloud OAuth client. Copy the redirect URL from the n8n credential into Google Cloud, set your public URL on self-hosted instances, and update n8n if you're on an affected version.

n8n schedules use n8n's own timezone setting, not the server clock, and default to America/New_York. Set GENERIC_TIMEZONE for the instance and check each workflow's timezone setting, which overrides it.

This error means a node or Code node tried to read a field from data that doesn't exist, often because a previous node returned nothing or a different shape. Inspect the input data, guard against empty items, and make sure workers run the same version.

n8n 2.0 introduced many breaking changes: Code nodes run on task runners and can't read env vars by default, Execute Command is disabled, the Start node and Pyodide Python are gone, and Activate became Publish. Check the official breaking-changes list and re-enable or rewrite what you need.

A 503 'Workspace offline' page means your n8n Cloud instance is down or restarting, often after running out of memory or during an incident. Restart the workspace from the Cloud dashboard and contact support if it doesn't come back.