If one of your elements is hidden behind another element, you can change the stacking order to resolve this problem.
Select the item on top then select the Order button in the Toolbar at the top of the screen.
Then either click Backward enough times to move the problem element behind the other element, or select To back to send the problem element to the back of the stacking order.
If you press the 'All Layers' button, a panel on the left will open showing the full order of all elements on the artwork:
Here, you can click and drag elements to change their layer order:
