You have answered your question.
<"I have noticed that if I ping the connection server with cmd : ping horizon.vm.net it doesn't ping">
This is the reason why you see the error 'No network communication' when deploying machines in horizon pool.
All VMs in a horizon pool, must be added to domain. Possible while cloning the VM , your VMs are not getting added to domain and that is why it is not able to ping connection server.
Check your view composer service account setting if it has permission to join machines to domain in case you are using linked clone.
Additionally make sure new VMs are getting a valid IP in vCenter . If not, check network adapter/DHCP.
At all times you should be able to resolve your connection server using nslookup from VDI, you should be able to do telnet to your connection server over 4001.