0 Error: 0 Call to a member function get() on string

Hi Manisha, please help me with this: After select a plan in https://maiten.com/soluciones/asistencia-cloud#planes you will see other page where you have to insert your details, and after that, clicking in COMPRAR (SHOP) it should go to payment gateway but now is displaying this error: 0 Error: 0 Call to a member function get() on string

I share ftp details below.

Please help me. Thanks

NOTE: Please do not update payplans because we customize checkout page.