When a user's mobile device is lost, do one of the following. This should be carried out by cybozu.cn Administrators.

Changing the password logs the user out from kintone. As a result, kintone will no longer be accessible from the lost device. This also prevents kintone Mobile from sending push notifications to the lost device.

For the steps to change a user's password, refer to the following page.
Changing User Passwords

If client certificate authentication is used, disable and re-issue the client certificate in addition to changing the user’s password.
By disabling the client certificate, kintone will no longer be accessible from the lost device. All you need to do is to disable the client certificate for the user who lost the device, so other users will not be affected.

For the steps to disable a client certificate and then issue a new one, refer to the following page.
When Users Have Lost Their Devices with Client Certificates Installed

You can revoke access to kintone by deactivating the user in Users & System Administration.

For the steps to deactivate a user, refer to the following page.
Deactivating Users