On older versions of PowerPoint for macOS, AutoRecovery files (which are created when PowerPoint closes unexpectedly) may not get deleted properly when the file path contains a Unicode (international) character.
This issue is fixed in PowerPoint for macOS version 16.19.181109 or higher. You can check your version number by going to PowerPoint > About PowerPoint. (See also What version of Office am I using?) If your version of PowerPoint is older than this version, please update by going to Help > Check for Updates.
Once you update, you'll still need to manually clean up any files in the AutoRecovery folder by opening Finder clicking on Go > Go to Folder... (alternatively, you can also use the Command + Shift + G) shortcut and pasting the following path:
The folder <username> isn't a literal folder name. Instead, you replace it with whatever your user-name is on your computer.
Please review any files in that folder that you may want to save, and move or delete any files that you no longer wish to keep. If you do not remove them from that directory, they will continue to automatically open the next time PowerPoint opens.
New AutoRecovery files created in PowerPoint for macOS version 16.19.181109 or higher will no longer have this issue and will get deleted when you close PowerPoint with AutoRecovery files open.