Ever since the iOS 10 update, my wifi will not work on most of my apps. Was never a problem before the update. I've factory reset my phone twice to no avail.
I'm the same. WiFi range seems much reduced since upgrading, even after a soft and hard reset, and when it does connect it disconnects frequently (especially on public networks).
We noticed this problem with several mac we administer at the school at which I'm employed. The fix was to go into Setting -> Reset -> Reset network settings. This will cause the device to reboot. After that, you'll need to reconnect to your wifi network.