protected function validate_gateway() {

		$coupon_id = $this->coupon ? $this->coupon->get( 'id' ) : null;

		/**
		 * If payment is required, verify we have a gateway.
		 *
		 * For free plans the manual gateway is automatically used, whether or not it's enabled.
		 */
		if ( $this->plan->requires_payment( $coupon_id ) && empty( $this->data['llms_payment_gateway'] ) ) {
			return $this->error( self::E_GATEWAY_REQUIRED, __( 'No payment method selected.', 'lifterlms' ) );
		}

		$gateway_id = $this->data['llms_payment_gateway'] ?? 'manual';
		$is_valid   = llms_can_gateway_be_used_for_plan( $gateway_id, $this->plan );
		if ( is_wp_error( $is_valid ) ) {
			return $is_valid;
		}

		$this->gateway = llms()->payment_gateways()->get_gateway_by_id( $gateway_id );
		return true;

	}