1. Check if your charts or graphs were inserted within the slide master. If they were inserted there, delete them, then insert the charts or graphs onto the slide layout for each slide you wish to view them on.

2. Check the compatibility of the PowerPoint version you are using with the charts or graphs. If the chart or graph was created using a different version than the one you use, try converting the chart or graph into another file type such as JPEG.

3. Try ungrouping the chart or graph before uploading it to PowerPoint. Ungroup them, and then try formatting the graph separately to make sure they are in the right layout and size.

4. If the issue persists, check your chart or graph rights-managed settings. The general settings for chart or graph usage may be preventing you from viewing them on slides.

5. If all of these steps fail, try re-downloading/re-installing or upgrading your PowerPoint software. This may solve any underlying issues associated with it.