Lupo 1.2 TDI does not start and key is in the ignition lock

Since yesterday, my lupo doesn’t start anymore. The pressure storage is relatively new, the pump purrs as usual, but if you turn the key, nothing happens. And I can’t pull the key out of the ignition lock either… A few days ago, there was always a funny noise when the car started, before the car started. Can anyone here possibly have an idea what the problem might be?