Why I'm not able to create Community service access token through API?

Hello Azure team,

Recently I'm trying to create a video call app and I have used this ready made code for iOs:

https://github.com/Azure-Samples/communication-services-ios-calling-hero/tree/main/AzureCalling

My question is following:

I'm not able to create communication access token through this API:
https://nitinres.india.communication.azure.com/identities/identy_id/:issueAccessToken?api-version=2023-10-01

My request body is:
{

"scopes": [

"chat",

"voip"

]

}

I got response everytime:

{

"error": {

"code": "Denied",

"message": "Denied by the resource provider."

}

}

Could you please help me to resolve my issue? What the additional permission I'm missing?
Or please write here all steps with details so I can fix this issue...

Thank you!