Open Settings → Wi-Fi → network details → Forget This Network.
Step by Step
- Open Settings.
- Select Wi-Fi.
- Select the information button beside the network.
- Choose Forget This Network.
- Confirm.
- Reconnect later using the current password.
If That Doesn't Work
- Forgetting removes saved connection information from that device.
- This can help when an old Wi-Fi password is stored.