Hi,can any one help?Have just replaced the battery in my blue key and the doors are now not opening when i press the magic button!Battery is the correct one and round the right way.Any ideas as this is the only key i have and its now getting fiddley to open the doors with it as its quite worn..cheers jon

Have you tested the voltage of the new battery? It could be flat.

thanks for the reply,.battery seems fine red light on key flashes when i press the button but doors dont open.

The voltage needed to light the little led will be far lower than that required to broadcast the signal to open the doors. If the battery is almost dead it would light the light but not open the doors.
The cheapest option would be to replace the battery, if it proves not to be the issue then at least you'll have a spare for next time.
It could probably be lots of other things too but I haven't got a clue about those sadly.

Good luck.