Hello Ted. In the event PowerPoint won’t export your narrated presentation as a video, it is usually related to either media compatibility (i.e. the media cannot be exported), uploaded large embedded files, or conflicts with apps or add-ins. After opening your presentation, click File > Info. at the bottom of the Info section, you should see Optimize Media Compatibility click Optimize Media Compatibility. This will optimize all of your audio and video in your presentation for export. Next, close your presentation and compress your media. You can do this by going to File > Info > Compress Media which will compress or reduce the size of your media files and help eliminate your odds of an unsuccessful export.
If the issue persists, launch PowerPoint in Safe Mode (use Win + R, then type powerpnt /safe) to eliminate the suspect add-ins as part of your difficulties. Further, close all unnecessary apps running in the background; you can do so in Task Manager (Ctrl + Shift + Esc). After that, verify that you have the latest update applied to your version of Office. Next, if the issues continue, perform a Quick Repair by going to Control Panel > Programs > Microsoft Office > Modify.
Here's the reference: Fix PowerPoint Error while exporting video
Note: I am providing this information as a convenience to you. The sites are not controlled by Microsoft. Microsoft cannot make any representations regarding the quality, safety, or suitability of any software or information found there. Please make sure that you completely understand the risk before retrieving any suggestions from the above link.
If the answer is helpful, please click "Accept Answer" and kindly upvote it. If you have extra questions about this answer, please click "Comment".
Best regards,