how to solve "clutch stroke insufficient"

[mikemike7252]

hello , every body recently i need to perform self-calibration to my Fiat 500 selespeed gearbox
because R gear always fail to engage, it just had not enough pushing force to do that
but it only show that message "clutch stroke insufficient" & then finished .
I want to ask if anybody can help me ?
I will be grateful for that.