The circuit board for the Husqvarna Automower's charging station is located inside the station itself. It supplies the loop with a signal and has a diode that indicates if there are problems with the loop.
Ideally, the diode should emit a steady green light, signifying that everything is in order. If the diode is off or shows a colour other than green, it can indicate various issues depending on the colour displayed. If the diode is completely off, it's not receiving power.
Start by ensuring that the transformer and low-voltage cable are properly connected and that there is power in the outlet. A non-working transformer could be the issue. If the transformer outputs the expected voltage but the lamp remains off, we would advise checking the low-voltage cable for damage.
If no damage is found, the circuit board is the likely culprit and should be replaced. Remember, after replacing the circuit board in the charging station, you'll need to pair your Automower with the new board.

For Automower 220AC and 230ACX, this is done by changing the PIN code. On newer Automower models, the option 'new loop signal' is found under the security settings.