When client certificates on users' mobile devices expire, you need to do one of the following. This should be carried out by cybozu.cn Administrators.

If users want to continue to use the client certificate authentication after the expiration dates of their client certificates, you need to re-issue their client certificates. You cannot extend the expiration dates of existing client certificates.
For details on how to re-issue client certificates, refer to Configuring Client Certificate Authentication.

To disable accesses to mobile devices after the expiration dates of client certificates, do one of the following.

• Change passwords/Deactivate client certificates
  Changing the password causes the user to be logged out and kintone is no longer accessible on the device. This also prevents kintone Mobile from sending push notifications to the lost device.
  In addition to the password change, it is also necessary to deactivate the client certificate.
  Changing User Passwords
  Stopping the Use of Client Certificate Authentication
  

• Deactivate the user
  You can also disable access to kintone by deactivating the user in Users & System Administration.
  Deactivating Users