Customer.io Common Errors

Overview

Diagnose and resolve common Customer.io integration errors, delivery issues, and API problems.

Error Categories

Authentication Errors

Error: 401 Unauthorized

{
  "meta": {
    "error": "Unauthorized"
  }
}

Cause: Invalid Site ID or API Key Solution:

1. Verify credentials in Customer.io Settings > API Credentials
2. Check you're using Track API key (not App API key) for identify/track
3. Ensure environment variables are loaded correctly

# Verify environment variables
echo "Site ID: ${CUSTOMERIO_SITE_ID:0:8}..."
echo "API Key: ${CUSTOMERIO_API_KEY:0:8}..."

Error: 403 Forbidden

Cause: API key doesn't have required permissions Solution: Generate new API key with correct scope (Track vs App API)

Request Errors

Error: 400 Bad Request - Invalid identifier

{
  "meta": {
    "error": "identifier is required"
  }
}

Cause: Missing or empty user ID Solution:

// Wrong
await client.identify('', { email: 'user@example.com' });

// Correct
await client.identify('user-123', { email: 'user@example.com' });

Error: 400 Bad Request - Invalid timestamp

{
  "meta": {
    "error": "timestamp must be a valid unix timestamp"
  }
}

Cause: Using milliseconds instead of seconds Solution:

// Wrong
{ created_at: Date.now() } // 1704067200000

// Correct
{ created_at: Math.floor(Date.now() / 1000) } // 1704067200

Error: 400 Bad Request - Invalid email

Cause: Malformed email address Solution:

// Validate email before sending
const emailRegex = /^[^\s@]+@[^\s@]+\.[^\s@]+$/;
if (!emailRegex.test(email)) {
  throw new Error('Invalid email format');
}

Rate Limiting

Error: 429 Too Many Requests

{
  "meta": {
    "error": "Rate limit exceeded"
  }
}

Cause: Exceeded API rate limits Solution:

// Implement exponential backoff
async function withBackoff(fn: () => Promise<any>, maxRetries = 3) {
  for (let i = 0; i < maxRetries; i++) {
    try {
      return await fn();
    } catch (error: any) {
      if (error.status === 429 && i < maxRetries - 1) {
        const delay = Math.pow(2, i) * 1000;
        await new Promise(r => setTimeout(r, delay));
        continue;
      }
      throw error;
    }
  }
}

Delivery Issues

Issue: Email not delivered

Diagnostic steps:

1. Check People > User > Activity for event receipt
2. Verify campaign is active and user matches segment
3. Check Deliverability > Suppression list
4. Review message preview for errors

# Check user exists via API
curl -X GET "https://track.customer.io/api/v1/customers/user-123" \
  -u "$CUSTOMERIO_SITE_ID:$CUSTOMERIO_API_KEY"

Issue: Event not triggering campaign

Cause: Event name mismatch or missing attributes Solution:

// Check exact event name in dashboard
// Event names are case-sensitive
await client.track(userId, {
  name: 'signed_up',  // Must match exactly
  data: { source: 'web' }
});

Issue: User not in segment

Cause: Missing or incorrect attributes Solution:

1. Check segment conditions in dashboard
2. Verify user has required attributes
3. Check attribute types match (string vs number)

SDK-Specific Errors

Node.js: TypeError - Cannot read property

// Wrong - SDK not initialized
const client = new TrackClient(undefined, undefined);

// Correct - Check env vars exist
if (!process.env.CUSTOMERIO_SITE_ID) {
  throw new Error('CUSTOMERIO_SITE_ID not set');
}

Python: ConnectionError

# Handle network errors
import customerio
from customerio.errors import CustomerIOError

try:
    cio.identify(id='user-123', email='user@example.com')
except CustomerIOError as e:
    print(f"Customer.io error: {e}")
except ConnectionError as e:
    print(f"Network error: {e}")

Diagnostic Commands

Check API Connectivity

curl -X POST "https://track.customer.io/api/v1/customers/test-user" \
  -u "$CUSTOMERIO_SITE_ID:$CUSTOMERIO_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{"email":"test@example.com"}' \
  -w "\nHTTP Status: %{http_code}\n"

Verify Event Delivery

curl -X POST "https://track.customer.io/api/v1/customers/test-user/events" \
  -u "$CUSTOMERIO_SITE_ID:$CUSTOMERIO_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{"name":"test_event","data":{"test":true}}'

Error Handling

Error Code	Meaning	Action
400	Bad Request	Check request format and data
401	Unauthorized	Verify API credentials
403	Forbidden	Check API key permissions
404	Not Found	Verify endpoint URL
429	Rate Limited	Implement backoff
500	Server Error	Retry with backoff

Resources

• API Error Reference
• Troubleshooting Guide
• Status Page

Next Steps

After resolving errors, proceed to customerio-debug-bundle to create comprehensive debug reports.