No connection to WLAN

Hi Guys, i have a big problem. since a few days my macbook cannot connect to wlan at all. no chance with a cabel aswell.

my macbook finds the right router and shows me that is has connected but i cannot open any website at all. and i hvae to give it the password after every restart. i tried everything but nothing helps. everything else works.(programms ect.)

the reason for that problem could be that i wlaked trough the city by very cold temperatures having my macbook just in my backpack. after i opened it after doing that i had to reset the time and the date.

pretty wired! do you guys have any ideas what i could do now??

thanks for your help!!