Hi @bbilal,
As you are receiving a 401 error this indicates the 30-day expiration time of your access token has passed
I would recommend following step 7 from our post here - Public Postman Collection Now Available.
The method above places the authorisation header in all child folders and endpoints used.
You can also use our Get Ouath access token endpoint to generate a new token.
I hope this helps & please let us know if you require any further assistance.
Kind regards