Access token works in Postman but not in Azure Function

Hello community, I need your help to understand better what is going on here.

Situation - desired result I developed, in python, an Azure function that:

• is triggered by a POST request
• use the package "requests" to get an access token (for service principal) for the PowerBI REST API use this access token to send a Post request to PowerBI

Postman If I run the exact same requests in Postman, I am able to

• retrieve the access token
• use this access token to send my POST request Everything works fine.

Azure Function

• the token is retrieved correctly
• the POST request to the PowerBI API fails with a 403
• If I copy and paste the access token retrieved by the script, and I used it in Postman, I also obtain a 403
• If I retrieve an access token with Postman, and I use it in the script, everything works fine.

Run/test section of the Azure function show me the following:

Looks like I haven't configured properly the network access of my azure function. Is there someone with experience in this field that can troubleshoot this error and explain what is going on? I did not set up the network infrastructure, so please, be as clear as possible:) Thanks! Luigi