Been there - done that. Even the emergency hydraulic relief system will not help if the bolt attaching the centreing damper to the nose leg is put in the wrong (counter intuitive) way - this jams the nose leg in the up position and nothing will make it drop. In fact I think there is a requirement to have a placard on the nose leg to that effect to check the bolt is in the correct (upside down) way.
Interesting to know if the aircraft was just out of maintenance or had work done on the nose leg recently.
Otherwise the retractable system on the Seneca, Lance and Arrow is pretty fool proof in terms of getting it down.