@t-p Ok, thanks, I will do this (I use customify). However I tried this with several themes including one of default ones (Twenty Fifteen I think) and the error was the same.
@tonyzeoli The problem is that the client do not want to convert to Powerpoint. For sharing Keynote it should be enough to publish it on the “Apple slideshare” – i.e. https://www.icloud.com/keynote/#<your_presentation> – as it is written in the official tutorial (https://support.apple.com/en-ke/HT207738). And as I said, it works perfectly with the old wordpress version. Nevertheless thanks very much for your reaction.
