My phone fails to connect to wifi networks it has been connected to before. When this happens, even if I reenter the password it will not connect. But if I restart the device, it connects to the network without my having to enter the password. This happens both at work and at home. It's a Samsung Galaxy Stardust running Android 4.3.
I don't know if this is an answer, but my problem has gone away. Here's what happened. I called TracFone tech support about this. The representative told me to shut the phone off, pull out the battery, and see if the battery had a red sticker on it. It didn't. Then she told me to put the battery back, and that the next step would be to do a hard reset. When I found that doing so would erase my settings and contacts and such, I declined. So I thought I had wasted my time. But the wifi problem has not happened since then. It's certainly not the only time I turned the phone off, so I have to think that taking the battery out for a couple of seconds reset something.