connecting to ssid witch captive portal will be disconnected when the connecting device is in idle

The wifi will bev disconnected and advice to input the code again, current config for seamless onine is always.

but when we are trying to use without captive portal the wifi will not be disconnected even if the device is in idle.

Hello,
From your description, I gather that the client devices connected to the SSID set with the portal authentication would drop the connection and need to be authenticated again. Is that correct.
May I ask how many client devices like mobile phones have this issue? It will also be helpful if you can tell us the the model of your authentication device. Is it that a gateway serves as the auth device while the APs broadcast WIFI or the APs work as the auth devices?