If the Identity Server SSL certificate is untrusted for any reason, it can be explicitly trusted by adding a XML element as a child of the ServiceDetails XML element in the Security.xml file:
There is already a ServiceThumbprint element, which needs to remain.To obtain the value for the thumbprint, view the certificate details when navigating to Identity Server in a browser. Get the Thumbprint from the Details tab. Copy and paste will sometimes introduce an invisible character in the content - it is recommended to transcribe the value and re-enter it to avoid problems.
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