Can you pull the cable from anywhere else along its length to see if it moves the derailleur. It may be that the cable has just slipped through the pinch bolt.
Yes cable still taught and mech moves when cable pulled.
Definitely the shifter.
@Constable_Savage started
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Can you pull the cable from anywhere else along its length to see if it moves the derailleur. It may be that the cable has just slipped through the pinch bolt.