like roc says, check the pothole protection system.
there is an actuation rod that the basket/mast pushes down on, that is connected to linkage that runs to both sides of the machine and connects to the pothole bars that drop down on both sides when the basket is raised off the base.
If anything in that linkage is worn or damaged it can alter the switch activation and not allow the unit to elevate or move. The display may even be showing a code during the fault condition.
If you do not find anything wrong with the pothole system then one other thing to look at is the control cable that runs through those pulleys on the side of the mast, there is a 16/5c cable that controls lift and lower, if the lift wire (white wire) has a break in it this can cause the lift to stop elevating when that break in the wire rolls over the roller.