Re: Samsung Galaxy S3 wifi connection problems since firmware upgrade
In the past, I've been able to easily remedy any such issues as you're now having, by calling my internet provider? tech support. You can also access your router & WiFi settings, where you can run a diagnostic test, etc., by typing the default gateway address ? for your router IP ? into your browsers address bar. That's what your providers tech rep. would have you do, then you can see signal strength, connection quality, etc., and run a test, or even boost your WiFi signal strength. Also, in your router & WiFi settings, it will show whether your phone is being recognized, or not.
Nonetheless, for your phone to suddenly not be connecting to your WiFi, since you did the firmware upgrade, it sounds more like a 'Settings' issue with your phone. Maybe double-check your Settings > WiFi ?