yes chewingyu, it sounds like the lift has a lock solenoid on the hydraulic control valve. It works with the operator presence system (the seat switch), when there is a presence in the seat it will unlock the system so it will work. More safety stuff the mfg thought was a good idea ;o). You could check the seat switch and see if there is a problem with it and/or the seatbelt (sometimes the seatbelt works with the seat switch in some models). If everything is ok there then it's more than likely the lock solenoid circuit.

Thanks for your reply Swoop223. Apparently, according to our vendor, it cannot be lowered manually.

unfortunately this is a byproduct of engineering by making hydraulic function electric over hydraulic. In most if not all cases there is a manual ability to lower the forks by use of a manual valve on the control valve but it is up to the operator to know this and is most likely shown in the operators manual.
If the operators have not read the manual and 'know their lift' then these incidents occur.
In cases like these if there is any doubt then the lift should be left as is, moved out of the way, and the forks flagged so no one will accidentally run into them and service personnel called out to correct the issue.
And to be honest, if there is a load on the forks it should be left there because there is no safe way to remove the load if it is on the forks. The 2nd lift would have to go underneath the pallet which would allow the pallet to tilt over and slide off the forks. Pallets are made the way they are for that very reason, keeping the forks inside the enclosure of the pallet frame helps keep it from tipping over if the load becomes unstable.
Check the operator manual and i think you'll find a reference about manual lowering, if not then yes, there is a problem with mfg engineering not providing thorough enough information. You can submit the concern and suggestion with the mfg if you like but i'm sure their response is to call your service provider if you have any issues.

Any response from anybody?

Upz post for response. Any manufacturers able to respond?