Bulk Upload Remarketing list issue 500 Internal Server Error

Hi Team,
I am trying to implement a workflow for Bulk upload of remarketing list into Bing Ads using the documentation provided here: https://learn.microsoft.com/en-us/advertising/guides/bulk-download-upload?view=bingads-13#uploading. So far I have been able to:
- Register my application
- Request user consent
- Get access and refresh tokens
The next step in this workflow is to get the URL for bulk upload of a .csv file by calling the getBulkUpload URL endpoint and once a URL is retrieved to upload the file and confirm that the upload happened successfully. Unfortunately I am getting a 500 internal server error when trying to end request to this endpoint. I am using Postman to construct the request and below I have shared the endpoint I am posting the request to:
https://bulk.api.bingads.microsoft.com/Api/Advertiser/CampaignManagement/v13/BulkService.svc