Granting Entitlements API not functioning as expected

Our user journey may allow users to experience multiple trials of our subscription product. We are using the RevenueCat API to grant users an entitlement for a custom time frame. Unfortunately after one successful request, subsequent requests no longer create a new entitlement for the user. Instead it returns successfully with the old entitlement that was granted.

Request 1 that grants the initial enitlement

 const resp = await fetch(
        `https://api.revenuecat.com/v1/subscribers/${userId}/entitlements/premium/promotional`,
        {
            method: 'POST',
            headers: {
                Authorization: `Bearer ${REVENUECAT_API_KEY}`,
                'Content-Type': 'application/json',
            },
            body: JSON.stringify({
                end_time_ms: Date.now() + 1000 * 60 * 60 * 24,
            }),
        }
  );

Returns 

{
  "entitlements":
    {"premium":
      {
        "expires_date":"2025-02-01T04:57:50Z",
        "grace_period_expires_date":null,
        "product_identifier":"rc_promo_premium_custom",
        "purchase_date":"2025-02-01T04:47:51Z"
      }
    }
}

After expiration, if we repeat the same request, I would expect a NEW entitlement with a new expiration to be created and activated. However, the same response comes back.

We would love to get this resolved, if possible! Thanks!