Not sure if this is a difference in the curl command for Windows vs. Linux, but
C:\>curl -u '8mfwsfr82lq76o4nzacx9wg414gppvox.i:fjxype9o0v9xh9ja14df9c42qw9dex05.s' -d 'code=p2q986nsbakwihca4c2jpgdw97zxq6hh.c:grant_type=authorization_code:client_id=8mfwsfr82lq76o4nzacx9wg414gppvox.i' https
But the bolded + underlined colons (:) above should be (&)
Other than that, it looks like you are doing everything ok at first glance. I would however uninstall/reinstall your addon given that you have shared your client secret publicly. In the future, it is usually better to obfuscate at-least half of the random characters to prevent them from being persisted.
Note, if you are using the Jive SDK (Node.js) if you update to the latest version, you can regenerate an OAuth 2.0 Client add-on with the following command:
jive-sdk create oauth2-client --oauthAuthorizeUrl="YOUR_REDIRECT_URL"
Hope this helps.