Fortigate or FortiClient Enterprise Management Server (EMS) was not found.

We recently deploy a Fortigate on last versión of 6.0 and all the 10 Forticlients in last version of 6.0.9, the configuration is recived by the Forticliente source the Fortigate, the FortiClient can pinging the Lan and Telemetry is enable on the interface, we just deploy 4 Forticlients registering to the Fortigate with a FortiClient Key and all running good like in version 5.6, but a few days later 1 PC says FortiClient Disconnected and the next message: Fortigate or FortiClient Enterprise Management Server (EMS) was not found.

We try to disconnect and connect again, but have the same error.

Can somebody help us? Thanks a lot!! Have a nice day!