Sometimes a bug can happen on a mac when it becomes impossible to add, select any chips or to create any wires, or to create any inputs/outputs.
If this bug happens to you and you don't want to exit and lose all your progress, the solution I've found is to click on one of the existing input/output rectangles (as if you want to rename it), and then everything works fine again.
Sometimes it is also impossible to click on these rectangles on one side. Then usually it is still possible to click on them on the other side. So to be protected from this bug, the first thing you should do when creating a new circuit is to add at least one input and one output to it.