It’s possible your Microsoft PowerPoint presentation is not successfully saving as a PDF due to a corrupted program. Here are some suggested steps to troubleshoot the issue:

1. Check if the PowerPoint program version is up to date and compatible with the operating system.
2. Try the default troubleshooting steps such as restarting the program and restarting the computer.
3. Test exporting a different presentation as a PDF to see if the issue is specific to the presentation or the program.
4. Try uninstalling and reinstalling the PowerPoint program.
5. If reinstalling the program does not help, check for any related program updates.