Client certificate calls are failing with 403.16 error

If all calls from the Veridium credential provider are failing with 403 error even though the certificate is valid and trusted, here’s what needs to be checked:

First of all, no related error will be found in Event Viewer, because this is happening at IIS level. So the logs that need to be checked are located in %SystemDrive%\inetpub\logs. An event like this can be seen:

image-20260326-123834.png

There are two possible reasons for this behaviour:

  1. Root certificate isn't trusted - the resolution is adding it to Trusted Root Certification Authorities Certificate store

  2. The Trusted Root Certification Authority store contains non-self-signed certificates - the following Powershell command identifies such certificates:

    Get-Childitem cert:\LocalMachine\root -Recurse | Where-Object {$_.Issuer -ne $_.Subject
    

If the above command returns a list of certificates, you must delete them or, for a safer approach, move them to the Intermediate Certification Authority store.


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