The drag canvas tool doesn’t work when the selected layer is hidden (closed-eye icon).
E.g. a hidden layer is selected, when I press space the hand cursor for dragging the canvas around doesn’t show up, but remains the forbidden sign (red circle slashed).
I think it’s a bug — dragging the canvas is not an editing operation, so the user should be able to drag regardless of the status of the currently selected layer, just like zooming.