First, please check the e-mail address registered by the member who made the inquiry.
(e.g., inquire directly by e-mail or phone, or locate it in the member’s membership information).
From the dashboard of the administration page, there is an item titled “Forcibly log out a member.” Enter the above e-mail address in the entry field there and press the “Logout” button.
You can then force the member to log out.