[Solved] Slides greyed out in slide pane?

[jw100a]

Sorry if this is a silly question, somehow I wasn't able to google it (not terming things properly?)

When I open my presentation, In the Slide Pane some slides are greyed out, while others aren't.
I haven't been able to spot a pattern or see any other differences between the slides.

What does that mean?

Thanks!

[RoryOF]

In the side pane on the left, right click on a greyed out slide and select "Show Slide" from the popup menu.

[jw100a]

D'oh!

I now noticed they are not showing up in the presentation mode either.

Thanks so much!