Can't export pptx in Keynote 6.2.2 to Powerpoint 2008 for mac v 12.3.6.
When exporting from Keynote 6.2.2, both pptx and ppt are available, but only files exported using ppt are read by Powerpoint 2008 for mac( v 12.3.6.) For files exported as pptx, Powerpoint returns error message that they aren't readable. Only first slide shows. While exporting, the blue progress line doesn't go beyond the middle of its track.
Trouble shooting done: All photos in presentation are jpegs, none are grouped. No special fonts or any animation. Cant export very small files to pptx. Export to pptx doesn't work on either IMac or Powerbook Pro. I also reinstalled Keynote and have restarted computer several times (once using Shift key for software repair). What's perplexing is that I was able to save to pptx previously. It's almost as if my Powerpoint 2008 is seen as a 97-2003 version. Any help would be appreciated.
Keynote 6.2.2
Powerpoint 2008 for mac v 12.3.6 (130206)
Operating system 10.11.15