If the screen says "WAIT" or "OFF," you have entered the wrong code too many times. You usually need to leave the radio powered on for an hour to reset the lock-out timer before trying again.
Sites like FreeRadioCodes or AutoCodes UK can often generate codes for specific Alpine models (especially older Mercedes-Benz units) based on that "AL" serial number.
The tool matches the unique identifier of your hardware to the security PIN assigned during production. How to Find Your Serial Number
You often have to pull the radio out of the dash to see the serial number on the sticker.