I'm using the Google My Business API in our project to fetch google review. The javascript script iterates over the list of locations and fetches review for each location. I know the code works because the majority of the locations return review perfectly.
Method Details here
Method : Post
URL : https://mybusiness.googleapis.com/v4/accounts/accountId/locations/locationId/reviews?access_token=token
The oAuth tokens are valid and not expired
The endpoint for listing reviews requires a GET method, not a POST. source: https://developers.google.com/my-business/reference/rest/v4/accounts.locations.reviews/list