Photoshop: When I hover over my image with the Spot Healing tool and click to drag my image goes away a gray screen appears with the wording no image selected

Can anyone tell my me what I’m doing wrong. When I select the spot healing tool it will pull up where I can adjust the sizes of the tool, however when I Hoover over my image and click to drag my image goes away a gray screen appears with the wording no image selected. Please HELP!