Because I have a tendency to pester certain people in the forum way too much, I will throw this one to the masses...

Got the new bolt and the battery is hooked up. It didn't even ask me to re-sync the key fob, though I don't use the buttons because they are in such bad shape.
Anyway, I am now getting Alarm Fault - and I forgot what that means. Owner's manual just says to contact dealer. That certainly won't be happening.

Any ideas? I am sure at least 10 of you have had this problem before. Thanks in advance for any help.

It’s normally a faulty sensor, it’s been said that locking and unlocking with the key sometimes clears it.
Is the car running otherwise ?
Ps, you can buy replacement cover for the buttons, get a pin under the edge and it lifts off, takes seconds to change

Alarm fault is usually the ultrasonic sensor in the ceiling I think? Might be worth removing it and checking its properly connected.

Yes, ultrasonic sensor, I showed you that when I was last there but I admit that was in June last year. It's the thing above your left ear when driving (as your steering wheel is on the wrong side), pull it out, unplug it, give the plug a squirt of contact cleaner (or even WD40, or whatever the French equivalent is, if that's all you have) and plug it back in. That's all I did last time and it seems to have lasted a while. Otherwise, I'm sure someone has a spare one kicking around so you can swap it.

Thanks to all. I remember the sensor. I will give it a shot with WD40== thankfully they do sell it here.