Does the pump make a noise when you try ? If it's making an inconsistent airiated noise, it may need fluid topped up then worked up and down to self bleed. It would beg the question....where has the fluid gone and why though ?
Without trying to be offensive and given your original question.....are you defo operating it right ? Does it come up so far and then stop ? If so, you may not be operating the trailer function.
It would be great to hear what kind of noise it's making.
If it is just clicking, it could be the solonoids. Is the battery ok ?
Try operating it with the engine bay open and listen to the pump unit....it's usually down one side of the engine or perhaps on the rear bulkhead inner transom.
