On my facelift 3.0 and I assume yours too, the rear vent has its own motor under the center console box.

The pre-facelift appears to get its air from the fan up front.

So yes it looks like your blower under the dash is not working.

Could be resistor but given the panel can cause this too I'd hook it up to diagnostics to be sure, if you can.

EDIT: Could be blower motor itself too. And I've been guilty of overlooking popped fuses also lol

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04 X5 3.0i auto
03 X5 4.6is