Ok, I found a few ppl with solutions to this problem, none of which worked for me. I tried resetting the phone under settings, and tried turning the Wifi off for a while and then back on, but to no avail.
I don't know if this will work for you, but it worked for me:
Changed the Wifi channel on the router to a lower one
Once I did this it started working immediately, and the Wifi signal strength was even much better than before.