Thank's for your answers,
Yes we have enough license for the agents, the IP adress of endpoint server is correct, we have no problem with other machines, execpt or this one that i have mentionned.
Yes Ronak, wa have unistall he agent and installed it again after we have used the clean agent program, but the problem still there, No trace of the machine on enforce server, (even if the services are running).
We still try to find a solution, we will try to see if it's AV.
Regards