How to reproduce:
1. Create a Dropbox API v2 app here: https://www.dropbox.com/developers/apps
2. In the created app console, create a local Redirect URI, for example, "http://127.0.0.1:65432/".
3. Open the SampleScene in the attached "DropBoxIssue" project
4. Open the "TestScript"
5. Set the 'ApiKey' and 'accessToken' strings to the Api Key and Access Token values generated in the Dropbox API v2 app dashboard
6. Set the 'LoopbackHost' string to the Redirect URI from step 2
7. Enter play mode in the Unity Editor
8. Check the Dropbox app storage

Expected results: "TestMessage" is logged to the console, no errors are thrown, the file is uploaded.
Actual results: ArgumentOutOfRangeException is thrown, a file is not uploaded.

Reproducible with: 2018.4.13f1, 2019.2.15f1, 2019.3.0f1, 2020.1.0a15

Additional notes:
1. A project could not be tested on 2017.4.35f1 due to compilation errors.
2. Removing DropboxCertHelper.InitializeCertPinning() will remove the ArgumentOutOfRangeException, but the file still won't be uploaded.