wi fi - Problem connecting my Xperia L to wifi..it shows Saved ,secured with WPA2..what should i do?

I tried to connect to my TP-Link ADSL2+ Modem Router (TD-8951ND) with my Xperia L, it worked fine the first three days, but now when I try to connect it shows "Saved, secured with WPA2" .

I tried almost everything but failed to connect. I tried resetting, restarting, changing password/id, keeping security open, manually adding the network etc.

How can I solve this?