I am getting the same issue in sandbox. Internal Server Error The server encountered an internal error or misconfiguration and was unable to complete your request. Please contact the server administrator, and inform them of the time the error occurred, and anything you might have done that may have caused the error. More information about this error may be available in the server error log. Even on paypal.com It says: Things don't appear to be working at the moment. Please try again later. Any guesses.
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