Slice tool won't let me slice any document into separate images

It's been months of my slice tool not working. It doesn't matter what document I am in, even a new one I just get the little circle with a slash through it symbol. I have to create and put out weekly emails for multiple clients and it's getting hard when i can't slice my document into separate images.

Sometimes when I copy an old file the previous slices will be there but I can't move them or anything and they often times end up disappearing. 

I have uninstalled and reinstalled and my app is up to date so I don't know what else to do.