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Could you add raw_output=TRUE, debug=TRUE parameters to get_data method to have the request and the response printed. In other words what does the method return when you call
get_data(list('GOOG.O','MSFT.O', 'FB.O'), list('TR.Revenue','TR.GrossProfit'), raw_output=TRUE, debug=TRUE)
Yes, HTTP status 503 ("Service Unavailable") indicates either a communication problem or a problem with the backend service.