"403 Forbidden error" while authenticating after upgrade to GS CU7

After the upgrade of Groupshare system from GS 2020 SR1 CU03 to GS 2020 CU7, we are getting "403 forbidden" error while trying to access the SDL login endpoint from our API.

However, using Postman, we are able to authenticate the credentials to obtain the access_token.

 The only variables that we set are
{TokenUrl}= "https://groupsharedev.sdlproducts.com/authentication/api/1.0/login"
{Username & Password}= Valid username and password
httpbody= "TMServerRestApi"

 Is there anything missing here which gives this forbidden error?

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