Case fields won't load

I installed the API and is working fine with the sales force leads object. But when I try to select case object it will not load.

I tried to load it manually (Refresh objects & fields) I see all the fields and objects so I linked everything with the form but when I save it, it won’t save properly. (after saving it won’t show any fields)

I think because I got lots of case field (150+)?

http://ww.wp.xz.cn/extend/plugins/gravity-forms-salesforce/