Dear @Cellcom,

Cellcom wrote

finally i tried to foget the client from Insight menu and then if client is trying to connect there appears an SSID with 'Network access denied' and if press to connect is says "Denied access to network. Connection failed"

Did you forget the client by clicking the following trash icon from Insight -> Known Clients?

Please navigate to Insight -> Known Clients -> Blocked to double-check if there are any clients blocked.

Dear @Cellcom,

Cellcom wrote

Yes, I had thoroughly checked that again and again, and there is no client blocked.

 

I just remebered there appreaed an option of forget, and i did that, thinking it will probably re-authorise the client, but now i dont have any clue to revert that or re-authorise the client, even though I am trying to connect it with non Portal based SSID as well.

Considering that you have configured MAC Filtering with whitelist, it's suggested to check the MAC address of your client and see if the MAC is changed. I guess that your client is using a randomized MAC address to join a new network, since you forget the client, it may use a new MAC address to join in.

More details about the randomized MAC address: 

https://support.apple.com/en-us/HT211227

https://source.android.com/devices/tech/connect/wifi-mac-randomization

https://support.microsoft.com/en-us/windows/how-to-use-random-hardware-addresses-in-windows-ac58de34-35fc-31ff-c650-823fc48eb1bc