Hi,
I think you need to add it in the input manager
edit/project settings/input
for up/down
make size 1 bigger and edit the added input, change the name (for example DpadV)
Set type to joystick axis and on axis select 7th axis.
for left / right add another input but use 6th axis.
Then instead of using Get Key Down you need to use Axis Event
Place the name you made in vertical (DpadV)
and also for horizontal if you have (else make it empty)
and set up the events