# Error code 502

<figure><img src="/files/PwKP8VNRkh39QQfNfwtO" alt=""><figcaption></figcaption></figure>

This issue indicates that the Web Application Firewall (WAF) cannot connect to the backend application server. To resolve this, verify the protocol used by the WAF to reach the backend server or whitelist the WAF IPs on the backend server.

Follow these steps to change the protocol:

1. Log in to the Prophaze Dashboard.
2. Navigate to the Settings tab.
3. Click the edit icon next to the domain name for which you want to make changes.
4. Check the endpoint and protocol.

Make sure to save any changes to apply the new settings.

<figure><img src="/files/rKm6cIiNXvozrWtTbKoK" alt=""><figcaption></figcaption></figure>


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