l have a 2002 307 HDi manual estate. The gearbox is refusing to shift into any gear when the engine is running. When the engine is off l can get any gear and the gear selector linkages are all connected. If l put it in gear and then start the engine (with the clutch depressed) l can move away as normal, but not change gear, and it makes a bit of a clanky sound..
Its baffling my mechanic, anybody got any ideas?

have u checked the clutch mechanism? for me sounds like the clutch does not engage properly or fully rather. Ask ur mechanic to check the clutch system fully & check whether it fully engages, or do this check for yourself. Bring car onto a flat surface & shift to 1st while engine being switched off, start it while pressing the clutch (fully down to the floor board) & then release parking break & check for following
whether vehicle is moving
RPM decreases a bit
does engine get loaded & start vibrate or rattle a bit

if any of become yes it mostly can be a problem with clutch & clutch does not separate engine & gearbox properly.