I would check below.
1. SVI defined on switch for vlan map to SSID & ip-helper address is configured under that vlan.
2. Dynamic interface vlan map to SSID is permitted in WLC-SW trunk port
3. SSID assign dynamic interface configuration include your primary/secondary DHCP server info
4. Under WLAN advanced tab, "DHCP Addr Assignment" is ticked.
HTH
Rasika
*** Pls rate all useful responses ***