Today, we were having trouble saving a PowerPoint slide deck as a set of PNG files.
The error message said:
Sorry we couldn't find slide1.PNG. Is it possible that it was moved, renamed, or deleted?
After trying to copy the slides into another deck to replace the original deck, the same problem existed. Saving in PPTX format was fine. Curiously, saving individual slides was also fine.
I found a few blog posts online that said it might be to do with an embedded period in the filename. That wasn't the case but it gave me the clue that I needed.
The filename had a space before the .PPTX. This caused the error above. Removing the space fixed the issue. So if you see this issue, check if there is any nonstandard issue with your filename.
Hope that helps someone (including me the next time I run into the issue and can't remember what the problem was).