Microsoft Office PowerPoint uses a Slide Master that can apply changes across an entire presentation -- until it doesn't. Sometimes changes applied to the Slide Master don't affect the rest of the presentation. Learn to apply your changes to all the slides in the presentation, if desired.
Reapplying the Master Layout
The Slide Master view is designed so that you can set up all the design elements you want before you start your presentation. But in real life, design often happens on the fly: people tend to decide they want things to look a certain way after they've already started creating slides. So once you've changed the Slide Master any new slides will look the way you want. The problem is you need to apply those changes to all the existing slides too. Once you're back in the Normal view editing the slides of your presentation, you can click on a slide in the pane on the left and then choose the Layout that contains the changes you made to the Slide Master. So, if you changed the Title and Content layout, click a slide with that layout, select the Layout button on the Home tab, and then choose the Title and Content layout. The Slide Master changes appear. You can speed up the process by selecting multiple slides at the same time and reapplying the layouts.