Can't setup new wireless SSID/access point on my VLAN

I have a VLAN that has been successfully set up on my GL-MT6000 (Flint 2). I am trying to add a wireless SSID to this VLAN. However, when I go to Network > Wireless in Luci and set up a new SSID and then select the VLAN as the associated network, the new SSID shows a message that states that the "wireless is not associated." The new SSID then remains disabled.

Can anyone help me understand why this SSID is not working? No devices are able to see or connect to the SSID and I really need to set it up.

Did you would like to add a new WiFi radio, probably for IoT devices?

If yes, please refer to this thread: