Does anyone know abt I-shift?

I have recently replaced the clutch Volvo ishift myself on a 2008 VN. After I installed everything back with new cylinder and clutch kits. I tried to do the calibration with VACADs, It got a error message said the "clutch operations too slow, and need check for air supply". I did check it was above requirement, and air to PMV is good as well. Does anyone expert can help? Thanks