When you try to connect the sixth one, is there any error message if it fails?
What are main network activities of 5 Wi-Fi users connected?

There is no error it just does not connect and as soon as i disconnect any device the 6th one get connected within a second... And other devices activites are just facebook not much usage.. Even i removed the sim and than try to connect still 5 can get connected

there is no error it just does not connect.. and as soon as i remove one device the 6th one get connected within a second... plus no major activities of other device just using fb on them.. i even removed the sim and than try to connect still not connecting more than 5.. and my firmware is also updated.. even changed channel to different numbers facing the same issue please help