Once your Reference Check has been closed or completed, you do not have the option to re-open it.
If you would like to request that your reference check be re-opened, please contact the organization you applied with directly. Note it's possible that an organization may choose not to re-open a reference check if they feel they have already received what they need to move you forward. Re-opening your reference check could prolong the hiring process as the organization waits for more responses from your references.