When you run an Ansible playbook on the control node that is not running on a Mac (e.g., you are running Ansible on RedHat, Ubuntu or SUSE), you get this error: "Failed to connect to the host via ssh: percent_expand: unknown key %C\r\n", "unreachable": true". How do you debug your playbook to get it to run?
The problem may not be in the playbook. It may be in the ansible.cfg file if the ansible.cfg file was created for Ansible to work on a Mac OS.
Find the ansible.cfg file. Back it up. Comment out the stanza with "ansible-ssh-%%C". This stanza is appropriate for Mac OS deployments of Ansible.