XTrail Siren Communication Fault

That's a tricky one. A communication fault could stem from a few things. Have you checked the fuses related to the alarm system? Also, has the car been in an accident recently, even a minor fender-bender? Sometimes that can jar things loose and cause intermittent issues. It seems odd for a 2022 model to have wiring issues already, but it's not impossible.

I did check the fuses; they all seem to be in order. Regarding accidents, nothing recent. Could a software glitch also cause this? Is there a way to force an alarm system reset, or would it only be possible to do with an error code?

A software glitch is always a possibility, though less likely than a loose connection. Unfortunately, there's no simple 'reset' button for the alarm system like you'd find on a router. Since it's a communication fault, and you've checked the fuses, it really does point to a wiring issue between the siren and the car's computer. At this point you would need to take it to a workshop!

Thank you for confirming my suspicions and for the assistance! I took it to the workshop. As you predicted, there was a loose connection. They fixed it for 95€. Everything works again.