I am using (DMA softlab) Radius manager4 with mikrotik RB493 as my DHCP server. I created NAS server on the RM4 where all the login details of my clients are, when you try to browse logon page comes up and it allows you to login well. My challenge now is that when a customer's account has expires, or customer using wrong password; or trying to log in when he/she has already login etc. the log on the MK does not show their various error. The only error message you could see display on the MK log is Radius server is not responding even if the account has expired or you are using wrong password.
Please i need someone to help me out on this issue. Thanks to you all.

It is the correct message if you are using a new version of RADIUS Manager. It uses FreeRADIUS v2, and that added a new Access-Reject delay of about a second.

Change your radius timeout to 2 seconds.

Thanks so much SurferTim for your advice, it is working well.