Issue with OAuth Access token generation/retrieval from 3rd party OAuth provider . Common problems include

1) Token is retrieved but when a outbound web service call is made with the token it fails with Authentication error

2) Token retrieval fails with the error

The request body must contain the following parameter: '<parameter_name>'.

3rd party OAuth provider is expecting additional parameter apart from what is defined in OAuth application registry

1) Check with OAuth provider to confirm what is the required parameter for the OAuth flow

2)Extend or copy 'OAuthUtil' script include, and then reference your version from the OAuth API Script field on the Application Registry form for third-party OAuth providers. The custom script include name must start with OAuth.

add the required body parameter in this method:

preprocessAccessToken: function(requestParamMap) {
requestParamMap.put("<parameter_name>", "<value>");
},

For example if the OAuth provider requires "resource" parameter with value "https://outlook.office365.com" the code would look like:

preprocessAccessToken: function(requestParamMap) {