"Internet may not be available"?

I got this phone a month ago, it worked perfectly fine (except for that screen glitch, but its fixed now), a few days after I fixed it.... I join my house wifi, but every few seconds it will have "!" beside the wifi signal, and when I go to settings it says "Internet may not be available", I quit wifi then join back, but it still says that? Can someone fix this? I saw plenty of other complaints with this problem too!