author upload Bug problem

I just install the WordPress ur plug in was the first and the only one I have in plug ins

when author trying to upload an image rom media botoun appear this msg :

“”An error occurred in the upload. Please try again later.””

image:
http://s23.postimg.org/xchz761h7/Untitled.png
the user role is fine like should be how to solve ?

https://ww.wp.xz.cn/plugins/frontier-post/