Subaru immobilizer problem

[Tidoh]

picked a 2004 legacy estate up two weeks ago. All fine guy I bought it off said single button key fob didnt unlock the doors so had to use key to unlock then once in press button on sigma remote to start car. this worked fine until last Saturday. I had ordered a remote central locking kit off eBay but by chance pressed the sigma button and this locked all the doors this would be great except now I have a red key blinking on the dials next to the airbag light all the time???? and when I try to start I go through the procedure i.e turn key press button to turn sigma immobiliser off ( I hear the relay click for this) car will start but dies straight away and the red key symbol is still on. Ive checked the Battery in the subaru key reading 3.24v and when I insert this key the red light goes out around the ignition switch. My first foray into Subaru ownership and Im sure it will be something stupid but any help will be greatly appreciated