Can't rearrange slides

I'm new to this and sort of learning as I go. I'm using the plain white theme and I'm duplicating the Masters I want to use and putting in a company logo on them and in some cases changing the text boxes and media placeholders so the various slide will work for us. I've made or changed 3 master slides.

Then I grabbed the master and slide it down to the lower window that says "slides" to add it to my slideshow. In one case I use the "new" button at the top left corner to add a slide. Then I put the text I want in the text boxes I made, add media and they look good. Except I made them out of order. I have 3 slides and the middle slide should be the first one.

So I try to grab it and move it up. Won't move. Again I'm in the lower box that says "slides" on in the Master slide area. I googled this and everything I've read says to grab the slide and move it up or down. Well none of mine will move.

Am I doing something wrong or is this some sort of glitch. I would hate to have to delete them (a lot of work into them so far) and then recreate in the right order but why won't any of my slide allow me to rearrange their order?

Thank you for any help.

Susan