Well, can't tell the error for now, probably something with the structure, I will open the old PXML.xml with an XML Editor. I give my son a propre PXML (the one from arkanoid-remake"). It seems it works this time, as it's published (he pubished it without me)...
I think his PXML still contains mistakes, as I see no screenshot in the repo (and there are 3 in PND).