A couple of questions
1- is this unit new to you ? Have you had it a while ?
2- did it lift higher in the past?

I ask because some units had a lift shut off at set height for certain customers a limit switch
Mounted on mast to cut it off at a set height
Also had a button on the lift lever you pushed to over ride the lift limit of set height
If not then look at lift cyl tube for dents
If it was damaged it will only go to the height of the ding and stop the rod from passing
The damaged area