Stripe Webhook Signature Verification Failing

1. Wrong webhook endpoint secret (test vs live, or miscopied)
2. Raw body required for verification but parsed body used instead
3. Timestamp too old (Stripe rejects >5 min old)
4. Environment mixing (test webhook signed with test secret, etc.)
5. Multiple webhook endpoints with wrong secrets

Use raw body for Stripe verification:

// Express with raw body middleware
app.post('/webhook', express.raw({type: 'application/json'}), 
  (req, res) => {
    const sig = req.headers['stripe-signature'];
    const event = stripe.webhooks.constructEvent(
      req.body, sig, process.env.STRIPE_WEBHOOK_SECRET
    );
    // Handle event
  }
);

Verify you're using correct endpoint secret from Stripe dashboard.