The service principle name (Delegation) configuration has been set incorrectly.
Server connect URL:
SPN Identity:
The X.509 certificate is not in the trusted people store.
The X.509 certificate chain building failed.
The certificate that was used has a trust chain that cannot be verified. Replace the certificate or change the certificateValidationMode. The signature of the certificate cannot be verified.
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We had to change the certificateValidationMode to false to get in %appdata%\microsoft dynamics nav\90\ClientUserSettings.config to get in.