Salim,
I would check the edpa0.log file on the actual agent to determine the issue. I've seen a lot of issues around the EDPA service but none where the WDP starts but not the EDPA. It may be a permissions issue on the install directory of the agent. What version are you using?
I've seen issues where the JVM environment is corrupt and services are unable to start and by reinstalling Java, the issue is fixed but I really think that your edpa0.log files will accuratly tell the story.
The log files should be located under \Program Files\Manufacturer\Endpoint Agent
I would start looking in the logs for any SEVERE or WARNING type events