Peugeot 1007 key not working

[Vanin]

I lost one of the pair of keys on our 1007, the one with the electric sliding doors
Found it a year later in the garden where it seemed relatively unscathed. Tried it, it unlocked the car and opened the doors, put the key in the ignition and it turned the engine over but the engine would not fire.
Put the other key in and the engine fired up straight away
I could understand it if the battery had failed or none of the functions worked but it seems odd that everything seems in order apart from the engine firing up
Is it a new expensive key from Peugeot or could there be a simple answer?

[bearman68]

The circuit board inside the key has gone tits up. Assuming it a remote key, the circuit board has 2 functions. 1 is the remote bit, and the other is the immobiliser bit. To get the immobiliser to communicate, it needs to be powered by an induction loop on the key surround. I suspect the bit that powers the immo has gone belly up. (Not surprising if it's been in the garden for a year).
Most after market lock smiths can provide a key for this for around £150 I would think. A none remote one would be much cheaper.

[Vanin]

Thanks for confirming what I already thought. Just asked the question in the hope that it might be something simple.
Frankly I am amazed that all the alarm and door functions work and that the battery has not gone flat. You would have thought that if water had gone into the casing the whole lot would be junk.