I finally had to buy a “new” version, Powerpoint 2024. None of my older PP files will open! What kind of messed up pile is that? I am pissed to say the least.
???
You can open older versions in Compatibility Mode.
Some of the very old files, (I think prior to 2003) might still give you issues if you don't have the correct add-ins installed but you can also open them in Office 365 in your web browser and save them in the new format.