Recovered pptx returns as ppt and won't open

Hi

I deleted a pptx file from desktop and emptied recycle bin. Tried to recover the file and found several with semi-correct file name, but they won't open. PP says something like cannot open this filetype (different language) although file type seems to be ppt. It also says Autosaved in filename but they won't open from autosaved location either if I copy them there. File size is 15 Mb which is quite correct. Didn't find any software to open them.

Please any advice?

BR P