When i first open the game the default sand falls down perfectly fine but when i load a save such as a city save when i place sand it doesn't fall and nothing seems to work at all. Any ideqa of whats going on?
Maybe the save is paused. You can use the spacebar to pause / unpause it, or press the button in the very bottom right.
It also could be a strange air mode which prevents things from falling. Press 'y' to change the air mode until it says "Air: On". You can also change that in settings