Your payment processing system has stopped working, and customer transactions are failing between your WordPress site and Paddle or Stripe. This disruption can cost you revenue every minute it persists, so let’s fix it quickly.
Step-by-Step Fixes
Step 1: Check Your API Keys and Webhook Status
First, verify your payment gateway credentials are still valid. Log into your WordPress admin panel and navigate to your billing plugin settings. Look for sections labeled “API Configuration” or “Payment Gateway Settings.”
For Paddle users: Check that your Vendor ID and API Key match exactly what’s shown in your Paddle dashboard under Developer > Authentication. Even a single wrong character will break everything.
For Stripe users: Confirm your Publishable Key and Secret Key are correct. Visit your Stripe dashboard, click Developers > API Keys, and compare them character by character. Make sure you’re using live keys for production sites, not test keys.
Step 2: Test Webhook Endpoints
Webhooks are how payment processors notify your WordPress site about successful payments. If these fail, customers might pay but never get access to your service.
In your WordPress plugin settings, find the webhook URL (usually something like `yoursite.com/wp-json/paddle/v1/webhook`). Copy this URL and test it in your payment processor’s dashboard:
- Paddle: Go to Developer Tools > Webhooks > Test Webhook
- Stripe: Navigate to Developers > Webhooks > Test Webhook
If the test fails, your server might be blocking incoming requests. Contact your hosting provider to whitelist Paddle or Stripe IP addresses.
Step 3: Clear Plugin Cache and Transients
WordPress caching can sometimes interfere with payment processing. Clear all caches by:
- Deactivating any caching plugins temporarily (WP Rocket, W3 Total Cache, etc.)
- Going to your billing plugin settings and looking for a “Clear Cache” or “Reset Transients” button
- Using WP-CLI if you have access: `wp transient delete –all`
After clearing, try processing a test payment to see if the issue resolves.
Step 4: Check for Plugin Conflicts
Deactivate all plugins except your payment processing plugin. If payments suddenly work, you’ve found a conflict. Reactivate plugins one by one until payments break again. Common culprits include security plugins, firewall plugins, and other payment gateways.
Step 5: Verify SSL Certificate and HTTPS
Payment processors require secure connections. Check your SSL certificate hasn’t expired by visiting your site and looking for the padlock icon in your browser. If you see warnings, contact your hosting provider immediately to renew your SSL certificate.
Step 6: Review Server Error Logs
Access your server error logs through your hosting control panel (cPanel, Plesk, or custom dashboard). Look for entries containing “paddle,” “stripe,” or “payment” from the last 24 hours. These logs often reveal specific error messages that pinpoint the exact problem.
Likely Causes
Cause #1: Expired or Rotated API Credentials
Payment processors regularly rotate API keys for security. If you haven’t logged into your Paddle or Stripe dashboard recently, your keys might have changed without notice.
How to check: Log into your payment processor dashboard and look for any security notifications or alerts about API key changes.
What to do: Generate new API keys and update them in your WordPress plugin settings. Always use the copy button in your dashboard rather than typing manually to avoid errors.
Cause #2: WordPress REST API Disabled or Blocked
Modern payment plugins rely on WordPress REST API endpoints to communicate with payment processors. Security plugins or server configurations sometimes block these endpoints.
How to check: Visit `yoursite.com/wp-json/` in your browser. You should see JSON data. If you get a 404 or 403 error, your REST API is blocked.
What to do: Check your security plugin settings for REST API restrictions. In Wordfence, go to Firewall > Blocking. In iThemes Security, check Advanced > REST API. Whitelist payment-related endpoints.
Cause #3: PHP Version Incompatibility
Payment processing plugins require specific PHP versions to function properly. Running outdated PHP (below 7.4 in 2025) causes cryptographic functions to fail.
How to check: Create a PHP info file or check your hosting control panel for current PHP version.
What to do: Upgrade to PHP 8.0 or higher through your hosting control panel. Most hosts offer one-click PHP version switching. After upgrading, test your entire site for compatibility issues.
When to Call Expert Help
Contact professional support when:
- Error logs show database corruption or server-level issues beyond plugin settings
- You’ve tried all steps above and payments still fail after 2 hours
- Multiple payment methods (Paddle AND Stripe) fail simultaneously
- Your hosting provider confirms no server issues but problems persist
Professional WordPress developers can diagnose complex interactions between themes, plugins, and payment processors that aren’t obvious through standard troubleshooting.
Copy-Paste Prompt for AI Help
“`
I’m experiencing payment processing failures on my WordPress site. Here are my details:
- Payment processor: [Paddle/Stripe]
- WordPress version: [X.X]
- PHP version: [X.X]
- Billing plugin name and version: [Name vX.X]
- Error message (if any): [Paste exact error]
- When it started: [Date/time]
- Recent changes: [Any updates or modifications]
The payments were working before but now customers can’t complete transactions. I’ve already checked my API keys and they appear correct. What specific troubleshooting steps should I take for this WordPress payment integration issue?
“`
Remember, payment processing issues are stressful but usually fixable within an hour. Start with the simplest solutions first – most problems stem from incorrect API keys or temporary server glitches rather than complex technical failures.