Answer: Lost guide wire
The first thing before you cannot find guide wire or find it on CXR, would be a resistance to injection via the distal lumen and poor venous backflow from the distal lumen.
Lost guidewire during CVC insertion is a very under-appreciated complication and happens more frequently than thought.
Loss of the guide wire: mishap or blunder? - Br. J. Anaesth. (2002) 88 (1): 144-146.