Captive Portal Login Issues

Hello Dear Community ,
I hope you all doing good , I have an issue regard Captive portal logging in , we have FortiGate 200E and we configured captive portal via CLI to make maximum concurrent user to log in 1 only so that only 1 user log in , the issue here is that when users turn off Wi-Fi and turn on again or leave the company and come back again and try to login he can't log in because when I goes to firewall users monitor I find his user is already logged in and I have to DE authenticate manually so that he can login again , my question is how to avoid this issue and also tried authentication timeout but it does not work , so how do I configure it to DE authenticate the user automatically once he turn off the Wi-Fi .

thanks IN advance