I have read a bunch of posts, still cannot figure it out.

I am setting up a candy shop using version 1.38 with the French add-on portion.
Also added the 2 taxes Canadian add-on.
splittaxlines_1-11

The setup is almost all done except that when I want to pay using PayPal express, after zen cart bring me to the PayPal login page, after I to pay the screen then goes white ...

I tested the Curl using the Curlcheck util and the IPN using the IPNtest util, they both tell me they are fine ...

Any idea ??

Thanks