Getting 401-Unauthorized response while trying to Refresh Power BI Dataset using Postman API call!

Hello Experts,

I need an urgent help on one of the issues I am facing while trying to refresh the Power BI Dataset using POSTMAN.

Issue description -

1. Getting the Bearer Token -
This part is successful using the client id, tenant id, group id, dataset id and client secret I have been provided by the Admin team.
To generate the token I have used this URL : POST https://login.microsoftonline.com/{tenentId}/oauth2/token
Headers: Content-Type: application/x-www-form-urlencoded
Body:
client_id={clientId}
&client_secret={clientSecret}
&scope=https://analysis.windows.net/powerbi/api/.default
&grant_type=client_credentials

-> I am getting the token with no issues.

2. Refreshing the Dataset -
This part is giving me headaches!
Method: POST
url: https://api.powerbi.com/v1.0/myorg/datasets/{dataset-id}/refreshes
Headers Authorization: Bearer {token}
Body:
{
"type": "full",
"commitMode": "transactional",
"objects": [
{
"table": "TEST PO and Requisition"
}
],
"applyRefreshPolicy": "true"
}

But after applying all these, I am only getting - 401 Unauthorized!

Please help me in this or guide me if there is any workaround for achieving this refresh from a third party client.

Thanks in advance!

Regards,
PK