If the combined instrument panel shows the message Radar blocked See manual then it means that the adaptive cruise control's radar sensor cannot detect other vehicles in front of the car.
The following table presents examples of possible causes for a message being shown along with the appropriate action:
The radar surface in the grille is dirty or covered with ice or snow.
Clean the radar surface in the grille from dirt, ice and snow.
Heavy rain or snow blocking the radar signals.
No action. Sometimes the radar does not work during heavy rain or snowfall.
Water or snow from the road surface swirls up and blocks the radar signals.
No action. Sometimes the radar does not work on a very wet or snowy road surface.
The radar surface has been cleaned but the message remains.
Wait. It could take several minutes for the radar to sense that it is no longer blocked.