My typical problem is my file size is too large, I don't know why I can take a picture with my camera at the same setting in the same basic position and such and one file is bigger than another. I've gone through the tutorials here in the help thread, but the screen shots and such shown don't match up with what I see, I think it's because I have never installed Java on this system.
I recently bookmarked this site, haven't used it yet so no reviews but it's on my to-do list!
https://www.reduceimages.com/