The latest version of Keynote (version 6.5.3) opens Keynote presentations going back to version 3.
If the Keynote file is corrupt, there is nothing that can be done to open it, do you have a backup file?
If the Keynote application is corrupt, you can try the following procedure, perform all the steps in the order listed:
- Remove Keynote version 6.5, you must use an application removal tool for this procedure to work: Appcleaner is free, I use Appzapper
- Empty the trash
- Shut Down the Mac (Apple menu > Shut Down)
- Wait 10 seconds, then press the power button
- Immediately after you hear the startup tone, hold down the Shift key,
release the Shift key when you see the grey Apple screen
start up will take a few minutes longer than usual as the Mac is performing a software repair
- Restart the Mac normally, (don’t hold down any keys during startup)
- Install Keynote from the Mac App Store