That message is usually a communication error between the remote control unit and the receiver on the crane.
I suggest you re-pair the remote to the crane.
There should be a specific pairing procedure in your user manual, but it typically involves a sequence of button presses on both the remote and the crane's control panel.
If that doesn't work, then it could be a hardware issue with either the remote's transmitter or the receiver on the crane.
If none of these solutions work, I think you'd need to contact a certified Fassi technician for further diagnosis and repair!!