My iPhone is 4S (iOS: 6.1.3) and doesn't remember my Wi-Fi. So, each time I should select my network manually and enter the password.
Reset network settings? I did. Didn't work.
I had success with an iPhone 5 I just got on T-Mobile that was having the same issue. I selected my home wifi network, entered the password, after I put the phone to sleep the wifi password would need to be re-entered. What I did to fix the issue was to go into settings > wifi > other > then enter your wifi name and password and under security choose WPA.
My iPhone is 4S (iOS: 6.1.3) and doesn't remember my Wi-Fi. So, each time I should select my network manually and enter the password.
Reset network settings? I did. Didn't work.
Is SSID broadcast enabled on your router? If not, try this on your iPhone:
Settings>Wi-Fi>Choose a Network>Select your Network (tap on blue arrow)>Forget this Network
Now, go back to Settings>Wi-Fi>Choose a Network and manually enter your network login info.
I disabled the SSID broadcast on my router, and needed to take take these steps to allow my iPhone 4S to reconnect to my network automatically.
If your router is broadcasting your SSID, I don't know if these steps will help, but it might be worth a try.