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There is another question with the same tag which put me on the right track. Uninstall the printer. Then re-add it to the printer list by searching for it. When Windows finds the printer, tell WIndows to update the driver. If you do this then it will appear as 'Ready' instead of 'offline'. If you don't reinstall the driver then it will still report the printer as being 'offline'.
Hope this helps someone.