It sounds like the key needs reprogramming. When the battery was removed, it lost its memory. Visit the Dealership, and Auto-Electrician or an Alarm Installer.
Check microswitch in bonnet catch using a multimeter in continuity setting. To do this you will need to disconnect the microswitch connector and remove.
Watch the video:
https://www.youtube.com/watch?v=RpFbQQQnvO4
If you short the connector with a piece of wire and check the dash. This will simulate a switch closure. If it still shows bonnet open, then the wiring from the bonnet sensor switch is damaged and will need to be fixed.
alot of trimmers know how to do plastic welding and repairs to some plastics
ask or look up some of your local motor trimmers or bumper bar painters repair people