@Vincent-TP Thank you for your reply.

 

Let me explain, where i am facing trouble with;

 

1. My switch port where my TP Link AP is hooked is tagged with a VLAN number 3.
2. My NPS (RADIUS) and DHCP services are running on the single server and connected on the same switch. 
3. When i configure TPLink AP 683UR using RADIUS server with default configuration (without enabling and configuring VLAN with VLAN ID), it authenticates and gets IPs without any trouble.
4. However, as soon as i change my WiFi settings with enabling VLAN and assign a VLAN number 3 (or any VLAN ID), my client authenticates with RADIUS but doesnt get the IP from DHCP. I have tried to enable the dhcp in the interface setting of TPLink LAN configuration but didnt work. 
5. My client intiate DHCP broadcast through AP but on switch VLAN, we dont get any message from client through AP. Seems AP not forwarding any broadcast message (DHCP broadcat) to server and only allowing RADIUS communication.
6. This will lead our clients not to get the IP from AP when we enable VLAN setting for SSID. 

 

If needed any further details please let me know.

As mentioned above, yes both are on the same server, same switch and in same VLAN.