Do pptx files work for zShow ?

Do pptx files work for zShow ?

I've recently regen'd my license and have successfully tested the following using CURL:

'DOC','DOCX','ODT','HTML','RTF','TXT','CSV','XLS','XLSX','ODS', 'PPT','PPS','ODP'

BUT for some reason exactly the same code for PPTX fails with : 3832

When I look up that code (for zShow). It's not there, but further down there's a sample saying it could be a license issue and yet.PPT works fine...

(The other possibility was that the format was wrong but I've checked that it is supplied in the post as 'pptx')

Anyone any ideas on this I'm stuck.
Thanks