Thank you Kovah,
It might be Diskstation issue, but:
How come I can install Wordpress and Simple Invoice without problem in it and not Simple Plane?
I followed the instructions and verified every parameters and I can install it at the root of my site (but I can not see the pdf).
I thought that maybe someone had installed it in a Diskstation before, knowing what is the problem between IP and DS.
It is weird that all the other applications worked but not IP !
And I am sure that if I contact DS service they will tell me to contact the IP developers…
“the snake bits it tails” as we say in French…
Regards,
PS