How to fix

• Option #1: 
  • Tools > Accessibility Checker panel > right click on the image and select  "Set alternate text"
• Option #2: 
  • "Tags" panel > select the figure/image, right click and select properties > type down the alternative text that helps describe the image
• Option #3: 
  • "Content" panel > right click and select "Create Artifact"
• Option #4: 
  • Reading order > Show reading Order > select the image > add the "Image" tag > set the alternative text
• Option #5: 
  • Accessibility checker > Set alternative text (The tool will detect the images and allow to you to either add an alternative text or mark the image as a background artifact)