Problem next page or get more

i have more web site but i have problem on web postnews.media.

i try use page or count get more then 20 page error 500.

web is ok
http://domneng.com/khapi/get_recent_posts/?count=40

and this page error
postnews.media/api/get_recent_posts/?count=40

https://wordpress.org/plugins/json-api/