Problem entering code for radio on Renault Espace IV?

I know how I should enter the code for my radio (Renault Espace IV) but the procedure doesn't work.
Rather than accept each digit the radio just bleeps an error every time I try to change from zero. I can move from the first, to second, to third to fourth digit, using the button underneath the stalk control, but I can not set any value for a digit other than zero. This is very frustrating. Can someone please offer some helpful suggestions. Thanks