The expiration dates of the SSL certificates on both the client and server A common issue in Mutual SSL authentication is the expiration of SSL certificates. Checking the expiration dates of the certificates on both the client and server sides is crucial, as expired certificates will prevent successful authentication. Regular monitoring and timely renewal of certificates are key to maintaining uninterrupted Mutual SSL connections. Option A is incorrect because while browser compatibility is important, it is not a common cause of Mutual SSL issues. Option C is incorrect as network bandwidth, while important for overall connectivity, does not directly impact Mutual SSL authentication. Option D is incorrect because the version of Tableau Server is generally not related to specific SSL protocol versions for Mutual SSL authentication.