Installing Mollie payments API: unpermitted_parameters

Question

I am installing the Mollie payments API. Unfortunately, I get an unpermitted parameters: _method, authenticity_token (in the log). Here I would expect that a new window is opened that connects with Mollie.

I call the API by:

    if @reservation

        mollie = Mollie::API::Client.new('test_gUejkz43UkdeCauC22J6UNqqVRdpwW')

        payment = mollie.payments.create(
            amount: 10.00,
            description: 'My first API payment',
            redirectUrl: 'http://localhost:3000'
        )

The reservation is made and the site does not give an active error, which makes me think the API is not called. Does anyone see what I am doing wrong? I installed the gem, I use Rails 4 and use require 'Mollie/API/Client' on top of the controller.

Any suggestionis highly appreciated! Thanks