Eclipse 5443, something is up...

So my vehicle needed some serious work on the heater core so the whole dash was removed along with most of the audio in it. Its an older car and it has an eclipse 5443 head unit. Old Boston Acoustic speakers along with two sub amps, and a 500 watt amp. The only thing removed was the 4 front speakers, and and the head unit. Everything was working fire before hand. Now when I turn the car on I get an error message on the display screen of the deck that reads, Call 800 then a pause then C7300835. My first thought was this was some support phone number. So I called it and nothing happened. Anyways, Im kinda stumped as to what I need to do, aside from getting a new deck.