So if I read this right, you have wireless network, firewall, then DHCP server ?
First question – is the firewall operating as a layer 2 firewall, or layer 3 ?
If it is layer 2 (transparent firewall) then make sure there is a rule to allow the DHCP broadcast packets from the client through to the server, and the replies to come back.
If it is layer 3, then first you need to have a scope on the DHCP server for the wireless subnet, which needs to be a different subnet to the server, obviously as it is the other side of the firewall. Then you need to configure DHCP forwarding on the firewall to pass the broadcasts from the client to the DHCP server. Broadcasts do not pass over a layer 3 device, without some extra configuration. I don’t know this particular firewall, so I cannot comment on whether it has this capability or not, you will need to check in the manual. Look for IP forwarding, IP helper, or something to do with changing a broadcast to a unicast. This needs to be done on the firewall and not on the switch, as it needs to pass through that device.
If my original understanding of your setup is wrong, then please clarify, and either I will, or someone else will, have another go at answering.