Central locking……nothing goes!

Hello dear Volvo friends! I am not yet one of the Volvo owners but this could change already tomorrow I could get a V40 Bj 97 cheaply and I also like the car nevertheless there is a problem: the central locking is not possible and not at all. Neither via the key nor via the 2 remote controls nor via the switch over the radio, simply no function With the key in the driver’s door only this goes on the same also with the passenger door and suitcase raum. I’ve already read a lot of posts here in the forum but with the other threads only partially what doesn’t work. Could it just be the fuse or a relay? I don’t think the whole control unit is dead directly or would this be possible!?!!? Something else: the car has now almost 127000 down and the seller doesn’t know if the timing belt has been changed (is changed at 120000 or????) Which cover/folder can I open again after Would definitely change him if he doesn’t look so great anymore! (He’ll survive the almost 60km to my workshop) That’s it for now and hope for your help Thank you very much in front of Patrick