How do I get the slideshow to work on my ipad

If you select an album in the Photos app then at the top right of the thumbnail view in the album there should be a Slideshow button - does that not appear or not work ?

I don't think that you can - I haven't a way to do it anyway

Try creating a new album and adding all the other albums to it. That seems to work. It is not a perfect workaround but better than nothing. I don't know if the new album will auto update when the others are updated though.