I have this error message when I try to send an application to the application store
You can check Apple System Status , check iTunes Connect Twitter Account , or just search Twitter for iTunes Connect to see if the system is turned off.
I found that problems with the system will be displayed on the tweets of the people who use it in the first place (probably because it is not clear how you should report the shutdown).
Due to the maintenance of the Apple website, you cannot send the application to iTunes.