[Pki-users] Invalid Credential / User not found

After using the DogTag WEB Agent client once (based upon "preop.pin" value) the WEB Agent fail to continue to operate with error message= "Invalid Credential" . The "/var/lib/<instance>/logs/system" file reports an "User not found" error. NOTE: During the CA configuration setup the following Alert is displayed when the administrator certificate is installed: "This certificate can't be verified and will not be imported. The certificate issuer might be unknown or untrusted, the certificate might have expired or been revoked, or the certificate might not have been approved." Suggestions on what to try next will be appreciated? Ebbe Hansen @ SPYRUS "This message and any attached documents contain SPYRUS confidential and/or proprietary information and may be subject to privilege or exempt from disclosure under applicable law. These materials are intended only for the use of the intended recipient. If you are not the intended recipient of this electronic message, you are hereby notified that any use of this message is strictly prohibited. Delivery of this message to any person other than the intended recipient shall not constitute any waiver of any privilege. If you have received this message in error, please delete this message from your system and notify the sender immediately. Thank you."