const options = {method: 'POST', headers: {Authorization: 'Bearer <token>'}};

fetch('https://api.paddle.com/subscriptions/{subscription_id}/activate', options)
  .then(res => res.json())
  .then(res => console.log(res))
  .catch(err => console.error(err));

{
  "data": {
    "id": "sub_01hv915hmgnwqd9n5yxgy8t60c",
    "status": "active",
    "customer_id": "ctm_01hv8wt8nffez4p2t6typn4a5j",
    "address_id": "add_01hv914saqwe9wk1sbxyy9q7kq",
    "business_id": null,
    "currency_code": "USD",
    "created_at": "2024-04-12T11:30:29.648Z",
    "updated_at": "2024-04-12T11:31:10.027Z",
    "started_at": "2024-04-12T11:30:29.637Z",
    "first_billed_at": "2024-04-12T11:31:09.996Z",
    "next_billed_at": "2024-05-12T11:31:09.996Z",
    "paused_at": null,
    "canceled_at": null,
    "collection_mode": "automatic",
    "billing_details": null,
    "current_billing_period": {
      "starts_at": "2024-04-12T11:31:09.996Z",
      "ends_at": "2024-05-12T11:31:09.996Z"
    },
    "billing_cycle": {
      "frequency": 1,
      "interval": "month"
    },
    "scheduled_change": null,
    "items": [
      {
        "status": "active",
        "quantity": 10,
        "recurring": true,
        "created_at": "2024-04-12T11:30:29.648Z",
        "updated_at": "2024-04-12T11:31:10.029Z",
        "previously_billed_at": "2024-04-12T11:31:09.996Z",
        "next_billed_at": "2024-05-12T11:31:09.996Z",
        "trial_dates": {
          "starts_at": "2024-04-12T11:30:29.637Z",
          "ends_at": "2024-04-12T11:31:09.996Z"
        },
        "price": {
          "id": "pri_01hv0vax6rv18t4tamj848ne4d",
          "product_id": "pro_01htz88xpr0mm7b3ta2pjkr7w2",
          "type": "standard",
          "description": "Monthly (per seat) with 14 day trial",
          "name": "Monthly (per seat)",
          "tax_mode": "account_setting",
          "billing_cycle": {
            "frequency": 1,
            "interval": "month"
          },
          "trial_period": {
            "frequency": 14,
            "interval": "day"
          },
          "unit_price": {
            "amount": "500",
            "currency_code": "USD"
          },
          "unit_price_overrides": [
            {
              "country_codes": [
                "IE",
                "FR",
                "DE"
              ],
              "unit_price": {
                "amount": "700",
                "currency_code": "EUR"
              }
            },
            {
              "country_codes": [
                "GB"
              ],
              "unit_price": {
                "amount": "600",
                "currency_code": "GBP"
              }
            }
          ],
          "custom_data": null,
          "status": "active",
          "quantity": {
            "minimum": 1,
            "maximum": 100
          },
          "import_meta": null,
          "created_at": "2024-04-09T07:14:38.424504Z",
          "updated_at": "2024-04-09T07:15:53.950721Z"
        },
        "product": {
          "id": "pro_01htz88xpr0mm7b3ta2pjkr7w2",
          "name": "AeroEdit for learner pilots",
          "type": "standard",
          "tax_category": "standard",
          "description": "Essential tools for student pilots to manage flight logs, analyze performance, and plan routes, and ensure compliance. Valid student pilot certificate from the FAA required.",
          "image_url": "https://paddle.s3.amazonaws.com/user/165798/bT1XUOJAQhOUxGs83cbk_pro.png",
          "custom_data": {
            "features": {
              "aircraft_performance": true,
              "compliance_monitoring": false,
              "flight_log_management": true,
              "payment_by_invoice": false,
              "route_planning": true,
              "sso": false
            },
            "suggested_addons": [
              "pro_01h1vjes1y163xfj1rh1tkfb65",
              "pro_01gsz97mq9pa4fkyy0wqenepkz"
            ],
            "upgrade_description": null
          },
          "status": "active",
          "import_meta": null,
          "created_at": "2024-04-08T16:22:16.024Z",
          "updated_at": "2024-04-08T16:27:59.074Z"
        }
      }
    ],
    "custom_data": null,
    "management_urls": {
      "update_payment_method": "https://buyer-portal.paddle.com/subscriptions/sub_01hv915hmgnwqd9n5yxgy8t60c/update-payment-method",
      "cancel": "https://buyer-portal.paddle.com/subscriptions/sub_01hv915hmgnwqd9n5yxgy8t60c/cancel"
    },
    "discount": null,
    "import_meta": null
  },
  "meta": {
    "request_id": "8e6362d5-caaa-43d9-8ec5-f912c35b697d"
  }
}