Accessible Buttons in Storyline 360 - How do they work?

Hi There. I'm currently doing a lot of work regarding accessibility in Storyline 360. I've been using a screen reader and keyboard navigation to see how well my modules work in this format. 

The problem I'm having is how to advance onto the next slide using keyboard navigation. I usually use a button to advance to the next slide and I turn the default navigation controls off as I like being able to control when this button appears and when you can move on. 

When I use a screen reader it says use the command VO(caps)+Shift+Space to click a button. I get the click sounds but nothing happens. 

When I use the built in storyline keyboard navigation feature which is Alt+Ctrl+. again the slides don't move on. 

Even if I use the default navigation controls It still will not advance to the next slide in either of these ways.

I also have the same problem if there is a button to reveal content. The button just won't click using keyboard navigation. 

Can anyone help me?