Confusingly "PowerPoint Office 2010" is actually Office Picture Manager (OIS.EXE) - Not Microsoft's cleverest decision!
You will need to change the file association. If this isn't the click to run version you should be able to right click a pptx > properties. In Open With click CHANGE and then the Browse Button to find POWERPNT.EXE which should be in ProgramFiles\MicrosoftOffice\14.0
Make sure Always use this program is ticked and OK. If that's what you did I don't know!
If you do have click to run my advice is switch to the "real msi" version. This should be a free option.
If that doesn't help, then look at the website support.office.com how can I recover the file Recovery task pane.
https://support.office.com/en-US/art...9-3454d4a78585
Also assuming that all these suggestions do not help, you can try to use free PPTX Repair Kit or any other that you know. Maybe this will help. http://www.pptx.repair/