Beaten by technology

Technology is there to help us.  It should be simple to use and reliable.  However, it often defeats me.

This is an electronic picture frame.  Today I was loading some images on to it but, for some reason, it refused to display some of them - just showing a question mark instead.  I cannot work out why.  The files seem to be much the same as the other pictures loaded on to the device, in the same format, size in the middle of the range, titles in the same format and not especially long. 

I give up.  I'll just have to make do with the images it is willing to display, and I have deleted the rest.