Permission error on calendar/events with msGraphClient

I am developing a web part and would like to retrieve the calendar of my meetings room. Here is the response error:

{
"error": {
"code": "ErrorAccessDenied",
"message": "Access is denied. Check credentials and try again."
}
}

The request with MsGraphClientV3 :

Web Part Permission : 

In azure AD

The request work with PostMan with a token generated by myself but not with MsGraphClientV3.