3730800 - PKIX path building failed: unable to find valid certification path when calling SAP BTP authentication endpoint (OAuth token request)

• When calling the SAP BTP OAuth token endpoint " https://<subdomain>.authentication.<region>.hana.ondemand.com/oauth/token" from a third-party system. The request fails with an error: PKIX path building failed: sun.security.provider.certpath.SunCertPathBuilderException:unable to find valid certification path to requested target
• This issue occurs during OAuth2 token generation using the client credentials grant.
• The same endpoint works successfully when tested using tools such as Postman, but fails when invoked from the third-party system.

• SAP Business Technology Platform

PKIX path building failed, unable to find valid certification path to requested target, TLS trust, SSL handshake, certificate chain, root certificate, trust store, keystore, DigiCert G5, OAuth2, client_credentials, UAA, token endpoint, x509, Java cacerts , KBA , BC-CP-CF-SEC-IAM , UAA, Authentication, Authorization, Trust Mgmnt , BC-CP-CF-ROUTING , Cloud Foundry Runtime Ingress Routing Stack , Problem