Why won't 'clear defaults' work for gallery?

A

AC Question

I accidentally chose to 'always' open .jpeg email attachments using 'Gallery' on my Samsung Galaxy Core Prime. Now whenever I try to open a .jpeg image attachment it says it's 'unable to find image'.
Other image files (like .png will still open fine)
I reset defaults for Gallery but this hasn't fixed the problem. I'm still getting them same message while it still can't locate the image file.