Following on from what others have said - bootprelay (or any other form of 'dhcp helper' technology) is fundamentally an L3 function, and needs to run on the router of the network not a an L2-only switch.
Clearly if that switch has IP addresses, and is routing, then it is the right place for this to be applied - but it sounds like in your case you need to enable it on whatever device is the default router for your VLANs.