Iframe login resulting in Page Expired

So i have created two website one is for front page (WordPress) and the other one is for Member Area (Laravel) because of various reason .. i have to make the login button in front page to become popup iframe

So when i click login it will redirect me to member area (i'm using targer="_parent"). But when i tried to login it will return with this

Does anyone have idea how do i fix this?

PS : the website url is like this WordPress (testing.com), Laravel (members.testing.com)

via Chebli Mohamed