Ceph - When changing the Grafana password the Asible playbook fails with "Attempting to decrypt but no vault secrets found"

Issue

If we try to change the Grafana password using Ansible and following the documentation, and run the playbook as described in Step 4:

$ ansible-playbook -v site.yml

The playbook fails with the below trace:

TASK [ceph-validate : fail when dashboard_admin_password and/or grafana_admin_password are not set] *****************************************
Wednesday 19 May 2021  08:06:38 -0400 (0:00:00.615)       0:02:02.574 ********* 
fatal: [10.74.179.99]: FAILED! => 
  msg: |-
    The conditional check 'dashboard_admin_password is undefined or grafana_admin_password is undefined' failed. The error was: An unhandled exception occurred while templating '{{ grafana_admin_password_vault }}'. Error was a <class 'ansible.parsing.vault.AnsibleVaultError'>, original message: Attempting to decrypt but no vault secrets found