registration using xhr

[emath]

Hey,

I'm trying to implement registration with ajax/xhr request:

$.post({
    url: './register.php?do=addmember',
    data: formData,
    success: function(res) {
        console.log(res);
    },
    dataType: 'html',
    processData: false,
    contentType: false,
});

formData has all the data needed.

The user is successfully registered yet when I am refreshing the page, I am not logged in.
The session cookie is set successfully as well.

When I try to register the usual way, everything works fine.

What am I missing? is there something needed in the server side after the registration to acknowledge the cookie ?

Any help will be appreciated.