This unit has a tilt interlock system. Once the mast opens, you will only be able to tilt fwds about 2 degrees instead of the usual 6. Or, if you have already tilted fwds more than 2 degrees and then you lift the forks and the mast opens, lift will cut out until you tilt back to under 2 degrees. It is a design feature.

If the forks are raising ok with the mast open and then stop then the switch on the L/H tilt cylinder requires adjustment/replacement.