Contact your IT department or Mitsubishi Heavy Industries affiliates.
Your IT department may be able to grant you access to the leavers email so you can login to Coupa and
refresh the User roles. Alternatively, you can reach out to Mitsubishi Heavy Industries affiliates and request to change the contact information for you as a supplier and then "unlink" from the leavers account, then "relink" or invite using your email address.