i changed the battery after the screen said"smart key battery low" now it doesnt even open the doors, its the correct battery.

 

Are you certain the battery is in the right way round?

 

Thank's to everyone who replied to my question regarding my smart key fault,
After contacting a main jaguar dealer, i found out that just below the battery terminal inside the smart key, there is a small contact that can be "flattened" when closing after putting in a new battery, this tiny contact should be standing up so it makes a contact to the two half's when closed or you won't emit a signal.
This has now been rectified, so a big thank you to all who helped and to the jag dealer in Wolverhampton who spotted the error.