EM4000 Ver 3.1.1 is detecting a BigIP LTM as a non-F5 device

Hello.

I have an EM4000 Ver 3.1.1

I discovered a BIGIP LTM device but suddenly the EM lost the connection with this device.

I delete this device from the device list and i tried to discover it again. The EM sends the following status: Non-F5 Device.

any ideas about this behavior?

Thanks in advance...