First and foremost--I'm a Mastodon with these technological terrors called computers.
When I got my new digital camera I couldn't upload any pics to the forum. After some help from a daughter we found that the 'Quality' (pixel count ) of the pictures were too high and once the setting was adjusted downward just a bit I could upload any picture I wanted.
Just a thought--
No sure if it is the same thing, but I usually open them in paint and resize them down 50% if they don't upload first.