renault megan scenic 2001 2 lt rxe?

try this.
Climb in boot from inside with torch.
Look at the part of the catch which is fastened to tailgate.
If it has a small square button on the top. Stick a small flat screwdriver in the gap on the front edge of the botton and lift the button upwards.
It may help if someone presses the tailgate closed while you lift the button to take the pressure off the catch. Open tailgate while button lifted.
Works on some meganes but not sure if scenic is same.

ACB
April 2011