Verifying that the SPNs are correctly set for the Tableau Server service account A common issue in Kerberos authentication related to SPNs is incorrect or missing SPN configura-tion for the Tableau Server service account. The first step in troubleshooting should be to verify that the SPNs are correctly set and associated with the service account running Tableau Server. Incorrect SPN settings can prevent Kerberos from authenticating the server properly. Option A is incorrect because while ticket expiration is a factor in Kerberos, it is less likely to be the primary issue com-pared to incorrect SPN settings. Option C is incorrect as firewall settings, while important, are not the first aspect to check when SPN-related Kerberos issues are suspected. Option D is incorrect be-cause the client machines having Kerberos enabled is less likely to be the root cause of SPN-related issues in Tableau Server.