This is a common issue with Gmail triggers where the webhook connection can become stale without showing errors. The fact that reactivating the workflow processed the backlog confirms this was likely a webhook connectivity issue rather than authentication problems.
To prevent this silent failure in the future, I recommend:
• Set up an **Error Workflow** using the Error Trigger node to get notified when workflows fail
• Create a **monitoring workflow** that runs daily to check if your main workflow has executed recently - if not, it can alert you
• Consider adding a **heartbeat mechanism** - have your workflow send a daily “I’m alive” message so you know it’s running
You can find similar cases and solutions in the [community.n8n.io]( No workflows are working in Active mode ) forums where other users experienced webhook triggers stopping without errors. The key is building proactive monitoring rather than relying on error logs alone.