can't use panel, I see source code instead [#2758429]

Hello,
I installed openoutreach 3 days ago, but I'm not able to solve a problem.
When I click button for change layout of homepage, instead of the normal page I see the source code!
I don't paste it all, but just for your informations:

[{"command":"settings","settings":{"basePath":"\/farrotest\/","pathPrefix":"it\/","ajaxPageState":{"theme":"outreach","theme_token":"x3Rk72yQuObMsu0-AHZen1crnrIbBGLTFeEgImW7mjs"},"jcarousel":{"ajaxPath":"\/farrotest\/it\/jcarousel\/ajax\/views"},"CTools":{"dependent":{"panels-layout-category-AT-Responsive-Panels-1-column":{"values":{"edit-categories":["AT-Responsive-Panels-1-column"]},"num":1,"type":"hide"},"panels-layout-category-AT-Responsive-Panels-2-column":{"values":{"edit-categories":["AT-Responsive-Panels-2-column"]},"num":1,"type":"hide"},"panels-layout-category-AT-Responsive-Panels-3-column":{"values":{"edit-categories":["AT-Responsive-Panels-3-column"]},"num":1,"type":"hide"},"panels-layout-category-AT-Responsive-Panels-4-5-6-column":{"values":{"edit-categories":["AT-Responsive-P
...

and so on for 24k.
I tried to change theme, garland, Seven, but nothing.
Cache is disabled.
Log reports don't show anything of strange.
I'm using apache2.4 and also nginx, I don't know if this is important.
Let me know please.