If you get a 400 error for Authorization Code when you are trying to get the refresh and access tokens, go back to the step before your user authorization page and use this url instead. Authorizing and then getting that authorization code from the localhost url helped with errors down the line.

https://www.strava.com/oauth/authorize?client_id=[INSERT CLIENT ID]&response_type=code&redirect_uri=http://localhost/exchange_token&approval_prompt=force&scope=activity:read_all,read_all,profile:read_all