HELP PLEASE: Can't get simple button to work

I'm trying to build a fairly simple screen (tabbed interation style) where the learner clicks on one of several buttons that then displays the relevant layer with further options.

I want the button selected to be visibly different to the rest so that the learner knows which one they currently have selected. I also want a different visited state so that they know which ones they have already looked at.

I thought that this should be really simple using the standard Normal, Selected and Visited states & layers but I cannot get them to work. When you click on the button it goes to selected fine but then when you click on a different button, the one previously selected does not change to visited, it stays on selected.  If I click the button again it then goes to visited.

Any help really appreciated. I've attached the story file. Its the 'Test Menu Layer' layer that hold the buttons.