Kerberos Error Code: 0x7 KDC_ERR_S_PRINCIPAL_UNKNOWN (dsforum2wiki)
This issue can occur if no SPN has been set for a specific service, please refer to the resolutions in the section 0x7 - KDC_ERR_S_PRINCIPAL_UNKNOWN of the following article to troubleshoot the issue.
Service Logons Fail Due to Incorrectly Set SPNs
To understand, detect, correct, and verify SPN information, reference the following article: Service Principal Names (SPNs)
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