Aye Steve,
Sometimes the problem is that the size of the image is restricted and if you have an image that is too large or you try to upload multiple images that have a total size greater than allowed they too will be rejected.
Software to alter the image size is available, but you have to know how to use it and then there is the Windows, Android and ?, operating system differences to further confuse.
I don't envy you posting the sticky, but good luck. Thank you for trying.
Good health, Bill