Returns the currently cached access token. If no access token was previously cached, or if the current access token is expired, then a new one is generated and returned.
Thrown if clientId or clientSecret are null or empty. Thrown if there is an issue converting the credentials to a formatted authorization string. Thrown if authorization fails as a result of providing invalid credentials. Thrown if authorization fails and an HTTP error response is received. Thrown if there is an issue attempting to connect to PayPal's services. Thrown if there is an error with any informaiton provided by the . Thrown for any other general exception. See inner exception for further details.