Ansible, pushing configuration to cisco device

Hello,

We are trying to push a configuration to a Cisco router using ansible.
when we run a playbook we a re getting the following output:
ansible-playbook site.yml -i inventory

PLAY [Generate Router Configuration Files] *****************************************************************************************************************************

TASK [router : Generate configuration files] ***************************************************************************************************************************
failed: [x.x.x.x]  "msg": "Failed to connect to the host via ssh: Permission denied (publickey,keyboard-interactive,password).\r\n", "unreachable": true}
fatal: [x.x.x.x]: UNREACHABLE! => {"changed": false, "msg": "All items completed", "results": [{"_ansible_ignore_errors": null, "_ansible_item_result": true, "item": {}


PLAY RECAP *************************************************************************************************************************************************************
x.x.x.x               : ok=0    changed=0    unreachable=1    failed=0






Also: if I specificity the username to execute the playbook I got the following:

ansible-playbook site.yml -i inventory -u myuser

PLAY [Generate Router Configuration Files] *****************************************************************************************************************************

TASK [router : Generate configuration files] ***************************************************************************************************************************
 [WARNING]: sftp transfer mechanism failed on [x.x.x.x]. Use ANSIBLE_DEBUG=1 to see detailed information

 [WARNING]: scp transfer mechanism failed on [x.x.x.x]. Use ANSIBLE_DEBUG=1 to see detailed information

fatal: [x.x.x.x]: FAILED! => {"msg": "Failed to get information on remote file (/etc/ansible/TEMPLATES/myfolder/CONFIGS/RouterA.cfg): Shared connection to x.x.x.x closed.\r\n"}
        to retry, use: --limit @/etc/ansible/TEMPLATES/myfolder/site.retry

PLAY RECAP *************************************************************************************************************************************************************
x.x.x.x               : ok=0    changed=0    unreachable=0    failed=1


don't know why the connection is being refused.
we are new with ansible so I appreciate any suggestion.