Try resizing your photos
When uploading photos for your listing, images should be at least 330x330 pixels in size and should be uploaded in JPG or PNG format. Similarly, if your photos were taken with a Hi-Res camera, photos should not be any larger than 900x900 pixels, as that is the size of the images page, and 72 DPI (best for the internet).
If you have any issues uploading your photos, please check the size and format. There are many free websites that allow you to change the size and format of photos - here are a few options: https://www.img2go.com, https://resizeimage.net/, https://convertio.co/image-converter/.