cannot input code to unlock radio?

Hello.
My radio was working fine before I did this.
Renault clio 1.2 2003.
I have just tried to re set a sensor by disconnecting the battery.
I have re connected it but obviously the radio went off and time.
I can add the new time but on the radio 4 '0's are present and flashing. All good as I have the code.
I tried to put a 1 in the first 0 but all it does is beep. No number will activate into the slot?
Do I need to wait a while before putting it in or should it work straight away?