Below is the request I am passing on Google Playground as well as trying through code to fetch Access token and further data. Scope used here : https://www.googleapis.com/auth/fitness.activity.read
GET /fitness/v1/users/me/sessions?startTime=2019-12-05T00:00.000Z&endTime=2019-12-17T23:59:59.999Z&activityType=72 HTTP/1.1
Host: www.googleapis.com
Content-length: 0
Authorization: Bearer Auth_code
Your start time is malformed:
startTime=2019-12-05T00:00.000Z
You need hours, minutes and seconds:
startTime=2019-12-05T00:00:00.000Z
Request in OAuth playground:
GET /fitness/v1/users/me/sessions?startTime=2019-12-05T00:00:00.000Z&endTime=2019-12-17T23:59:59.999Z&activityType=72 HTTP/1.1
Host: www.googleapis.com
Content-length: 0
Authorization: ...
Response:
HTTP/1.1 200 OK
...