It sounds like a network issue.
Here's a few things you could try:
1/ See Chris Church's suggestion on this thread for a curl command to test the communication:
2/ Check you are using the correct port 5986 for https, 5985 for http
3/ Check your machine names are resolvable by your local dns.
4/ Check the windows event log on your managed hosts. When things are working there will be a login event.
5/ run with -vvvvv to see all the communication logging between ansible and your managed windows hosts.
3/ Check your machine names are resolvable from your Ansible master.
4/ Check the windows event log on your managed hosts. When things are working, there will be a login event. If there's no login event its probably not finished setting up the communications channel.
5/ run ansible-playbook -vvvvv to see all the communication logging between ansible and your managed windows machine.
Hope this helps,
Jon