Hi

I think the alarm (or immobiliser?) is in use. The LED is flashing always. And I read on the manual of the next link, that it dis-activates the car after 20 seconds - which would explain the "intermittent" problem I was having. It looks exactly like this

The key I have is not the same brand as what I linked - so I need to find where they installed it and see if I can swap it out for another one with working keys!

I should add... this all started happening after I disconnected the battery for a few days.

No receipt came with the car for this thing.