Yeah.. Not sure if the increased generator resistance has anything to do with it, i think if it was broken you’d get some kind of error message in the cars infotainment/diagnosis screen (the Ateca has one, pretty sure the XC40 does too somewhere?). It’s something the car should notice by itself. If you have, you could also try an OBD2 scanner and see if it spits out anything (not quite sure how well they work on the XC40).
As mentioned, i’d try a public charger, and from there you know your course of action. If it charges at a public station, the cable would be the next bet – in that case, i’d drive to Volvo and ask them to plug it in at their charging station with a different XC40, XC60 or something.
If the cable then does charge, it probably would be time to get out the multimeter and check voltages in your garage when you plug the car in (or wherever you plug it in).
If of course the car doesn’t charge at a public station (with a different cable than the one you’re using at home, of course), then it’s time to book an appointment since by that point then there’s probably nothing you can do yourself.