3810406 - Extension Setup Fails to Load "/appconfig.json" — Troubleshooting APPCONFIG_FETCH_FAILED and UNABLE_TO_VERIFY_LEAF_SIGNATURE Errors

During extension setup, the setup wizard displays one of the following warnings:

• "No appconfig.json found. Enter the required information."
• "Aucun appconfig.json trouvé. Saisissez les informations requises." (French)

In the browser Network tab, the extension-appconfig request returns the following response:

{  "success": false,  "error": [    "APPCONFIG_FETCH_FAILED - Error occurred while fetching appconfig"  ]}

In the backend logs, a TLS-related failure may also appear:

FAILED url=https://<hostname>/appconfig.jsoncode=UNABLE_TO_VERIFY_LEAF_SIGNATUREmessage=unable to verify the first certificatecause=unable to verify the first certificate

Note: The endpoint may load successfully in a web browser even when it fails for FSA. Browsers can mask certain misconfigurations, so a passing browser test does not confirm a correct setup.

Fig.1: Extension creation interface alongside the browser Developer Tools Network tab (F12), showing a failed configuration fetch.

Image/data in this KBA is from SAP internal systems, sample data, or demo systems. Any resemblance to real data is purely coincidental.

SAP Field Service and Asset Management

appconfig, extension configuration file, TLS handshake failure, certificate chain incomplete, intermediate certificate missing, config file not accessible, HTTPS 404 config, wizard setup error, CORS header missing, Sectigo intermediate , KBA , CEC-SRV-FSM-EXT , SAP Field Service Management Application Extension , Problem