How do I get the code in?

Thank you for the code for my ford transit custom radio.
1998 Model 3000 traffic two channel
serial no. MO46498
part no. 97FP-18K876-LA
When I put the code in, the keys on the panel don’t react as expected, I get a couple of dashes on screen and then it looks as if it’s going to take the code when put in but then goes into a “please wait” count down mode of 30 minutes and then asks for the code again.
Can anyone help again please to get the code in. I have tried to get manuels for the radio on line with no joy.
thank you
Barbara