I see this error when running playbook against my hosts, please assist
Failed to connect to the host via ssh: ssh: Could not resolve hostname hostname.acx: Name or service not known
Is the server name resolvable? Can the computer ansible see the server?
First step is to check if it is connecting without Ansible from your server
You can also use verbose when running the playbook. ( -vvv )
It may help you pinpoint the issue.
I suspect Its either a resolution problem as pointed by rajthecomputerguy or an inventory problem.