iPhone 4 won't connect to my home WiFi
why doesn't my older iPhone 4 connect to my home wifi when all other devices do; I receive "unable to join the network ---------". troubleshooting with another wifi network; it connects fine?
See the following Apple articles:
Connect to Wi-Fi on your iPhone, iPad, or iPod touch
https://support.apple.com/en-us/HT202639
If your iPhone, iPad, or iPod touch won’t connect to a Wi-Fi network
https://support.apple.com/en-us/HT204051
Recommended settings for Wi-Fi routers and access points
https://support.apple.com/en-us/HT202068
If you need help with your Wi‑Fi password