I am using the image assets that come with Adobe Captivate 2019 but when I play the slide or publish as an MP4 the images become red boxes. By reading posts, I have learned that the red boxes are created when the images are too large but I am slightly confused. Why would Adobe provide images that would cause an issue when publishing? How have you mitigated this issue? Any insights would be helpful.
Can also be due to a not updated graphics driver. Can you check? Lot of the images are indeed High resolution images. It would be a good idea to edit their size before inserting them into Captivate. You always get the best results when the inserted image is not resized in Captivate.