hallokblan
Does the release cable work when you pull it? If the release cable is not able to pull the safetly latch, then the problem may actually be that the lift system, though making a bit of noise when you press the button, is not actually "lifting' the Hi-Lo off the safety latch, which as you knoe, is necessary before you can lower it.
Does the lift motor just grunt when you raise it, or is it strong and makes the required 'whine' noise. If not, then here's a post to get you started.
http://www.hilotrailerforum.com/f28/no-lift-12v-65/
This may not be your problem, but we need to know about the safety latch before we can tell you more. Lets us know, and we'll help you figure it out
Neal