Potential Causes and Debugging Steps Firewall or Network Restrictions

Ensure there haven't been any recent changes to your network or firewall that might be blocking incoming requests.

Check if the IP addresses of Xero's webhook requests are being filtered.

Rate Limits or Request Blocking by Xero

Xero might have introduced new rate limits or validation requirements.

If your webhook is failing immediately after activation, Xero could be deactivating it due to consecutive failures.

SSL/TLS Certificates or DNS Issues

Confirm that your SSL certificates haven't expired or changed recently.

Run a DNS lookup to check if the webhook’s endpoint is resolving correctly.

Background Job Processing Logic

You mentioned that webhook requests are saved for background processing. Could there be a delay or misconfiguration that prevents the server from acknowledging receipt within Xero’s expected timeframe?

Webhook Request Format or Authentication

Verify if Xero has updated the request payload or authentication method required.

Try setting up a temporary endpoint that simply logs requests to verify what Xero is sending.