Hi @Cozza, Vanessa M ,
Did you check if this problem appear in all PowerPoint files or specific file? You can try to create a new PowerPoint file save in the desktop and check if this issue still exist in new PowerPoint.
Did you install any updates for PowerPoint or Mac OS recently?
You can also troubleshoot Office for Mac issues by completely uninstalling before you reinstall:
https://support.microsoft.com/en-us/office/troubleshoot-office-for-mac-issues-by-completely-uninstalling-before-you-reinstall-ec3aa66e-6a76-451f-9d35-cba2e14e94c0
If this problem only appear in sepcific file, try to save as the file in different file format.
Just checking in to see if the information was helpful. Please let us know if you would like further assistance, I'm glad to help you.
If the response is helpful, please click "Accept Answer" and upvote it.
Note: Please follow the steps in our documentation to enable e-mail notifications if you want to receive the related email notification for this thread.