Undefined Array key "link" error in srmklive paypal package in laravel

Question

I am a newbie. I have a saas project where I have used srmklive paypal package and it has the following code to create a new order. But when I click on the button, it shows an Undefined Array key "links" error. How to fix it so that on clicking the button, it redirects to the paypal payment page.

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public function onBoard(Request $request): JsonResponse
    {
        $plan = Plan::with('currency')->findOrFail($request->planId);

        if ($plan->currency->currency_code != null && ! in_array(strtoupper($plan->currency->currency_code),
            getPayPalSupportedCurrencies())) {
            return $this->sendError(__('messages.placeholder.this_currency_is_not_supported'));
        }

        $data = $this->subscriptionRepository->manageSubscription($request->all());

        if (! isset($data['plan'])) { // 0 amount plan or try to switch the plan if it is in trial mode
            // returning from here if the plan is free.
            if (isset($data['status']) && $data['status'] == true) {
                return $this->sendSuccess($data['subscriptionPlan']->name.' '.__('messages.subscription_pricing_plans.has_been_subscribed'));
            } else {
                if (isset($data['status']) && $data['status'] == false) {
                    return $this->sendError(__('messages.placeholder.cannot_switch_to_zero'));
                }
            }
        }

        $subscriptionsPricingPlan = $data['plan'];
        $subscription = $data['subscription'];

        $mode = getSelectedPaymentGateway('paypal_mode');
        $clientId = getSelectedPaymentGateway('paypal_client_id');
        $clientSecret = getSelectedPaymentGateway('paypal_secret');

        config([
            'paypal.mode' => $mode,
            'paypal.sandbox.client_id' => $clientId,
            'paypal.sandbox.client_secret' => $clientSecret,
            'paypal.live.client_id' => $clientId,
            'paypal.live.client_secret' => $clientSecret,
        ]);

        $provider = new PayPalClient();
        $provider->getAccessToken();

        $data = [
            'intent' => 'CAPTURE',
            'purchase_units' => [
                [
                    'reference_id' => $subscription->id,
                    'amount' => [
                        'value' => $data['amountToPay'],
                        'currency_code' => $subscription->plan->currency->currency_code,
                    ],
                ],
            ],
            'application_context' => [
                'cancel_url' => route('paypal.failed'),
                'return_url' => route('paypal.success'),
            ],
        ];

        $order = $provider->createOrder($data);

        return response()->json(['link' => $order['links'][1]['href'], 'status' => 200]);

    }



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I am a newbie and tried changing it to paypal-link but not working.