App Service Certificates: Path does not chain to a trusted anchor — Chain verification and trust issues

Problem description

I am experiencing an issue where the SSL certificate chain does not appear to be trusted by browsers or SSL Labs for my Azure App Service. The certificate was renewed and exported on September 14, 2026, and installed on my IIS VM for the domain users.pbstandards.org. Despite the certificate's private key being present and the chain being installed, the public site is reported as untrusted, suggesting a possible incomplete or incorrect certificate chain being served externally. I am seeking guidance on how to verify the certificate chain served publicly, identify potential issues with the exported certificate, and determine if any front-end services might be presenting the wrong certificate before traffic reaches IIS.

Environment

Azure App Service Certificates affecting users.pbstandards.org, located in the region not specified in the case information.

What I've already tried

I have reviewed the available case details and diagnostic information, verified that the renewed certificate thumbprint matches the one installed on my IIS VM, confirmed the certificate has a private key and validates locally, and checked that IIS HTTPS bindings and HTTP.sys are using the correct thumbprint.

Current status

I am seeking assistance to verify the certificate chain served externally, confirm whether any load balancers or proxies are terminating HTTPS before IIS, and understand if the renewal process through GoDaddy TLS Intermediate CA - R1v1 and Root CA - R1 is expected to produce a trusted chain. I would also appreciate guidance on how to identify the source of the trust issue and ensure the correct chain is presented to clients.