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.
We had to change the certificateValidationMode to false to get in %appdata%\microsoft dynamics nav\90\ClientUserSettings.config to get in.