WordPress Plugin WooCommerce, Custom Payment Gateway Settings Not Saving

Solution:

you have to call them on the constructor after theĀ init_settings();

    $this->init_settings();
    // Define user set variables
    $this->access_key = $this->get_option( 'access_key' );
    $this->title = $this->get_option( 'title' );
    $this->description = $this->get_option( 'description' );

edit:

you also need another action/hook, just at the end of the constructor, no need to create that new function that you came up with:

            add_action( 'woocommerce_update_options_payment_gateways_' . $this->id, array( $this, 'process_admin_options' ) );

edit 2:

sorry you already have it, my bad :p, dont realy know what happened there, glad its solved