97 Saab 900 - won't accept radio code

We lent our car to a friend that left a light on inside so drained our battery. We removed the battery, got it charged, installed the battery to find the CODE IN on the radio. We have the code but the car won’t accept it. When we put it in, nothing happens?! I don’t want to bring it to the dealer because they charge you to put in the code - why can’t I do it at home!?

You have “a” code. Perhaps it’s not “the” code.

Have you used this code before?

Yes, we have the code. We have used it in the past (it used to take it) and more recently, the dealer gave us the same code when we had to take it in.