If the element appears blurry in the Editing Window or does not show up in preview, please check if you have excluded the element from rendering. Simply check the layer side in the Properties Window on the right, and if there is a crossed-out eye icon, you can tell it is hidden from view. Click the eye icon to make it visible again. Alternatively, select the element in the Editing Window and click 'Exclude/Include in Rendering' from the dropdown menu.