G Pur 280 CDI no longer starts… desperation.

Hello, I’m close to desperation… My G Pur doesn’t start anymore. The history. It’s a 2009 edition PUR. 280 CDI. It’s only recently started via the emergency start button. According to ORC, this is due to a relay. The relay is ordered, but not yet there. In addition, I checked all the fuses in the center console. It’s all right. So it actually only seems to lie on the said relay…ABER, now it doesn’t start anymore! Tank is full, and a readout with a borrowed diagnostic device, did not produce any results or error messages. It is normal when trying to start, that’s all unfortunately not happening…! Can I have activated any immobilizer when checking the fuses? Does anyone have any idea how to get the boy running again? Desperate greetings from the Siebengebirge Daniel