vB5 Mobile API logged in user authorization

[PanterSi]

We have problem with current logged in user authorization with VBulletin Mobile API v5.
Description of the problem:
We're calling API endpoints from a PHP project that is on a different domain than the actual VBulletin forum. First, we call login and get back correct response with sessionhash and userid and store the data in session.
Then, when we call any method that requires current logged in user, we get this response: errors: "no_permission_logged_out"

What data do we need to provide with each API request, to authorize the logged in user on every API request? is there any additional request data to be passed, that is not described in documentation?

link to example request function that returns this error: http://vb5support.com/resources/mapi..._saveSignature