After reset still unable to join wifi

Reset Network Settings: As per your post you have done this...

If the above fails...

Reset All Settings: All settings—including network settings, the keyboard dictionary, the Home screen layout, location settings, privacy settings, and Apple Pay cards—are removed or reset to their defaults. No data or media are deleted.

1. Reset All Settings: Return iPhone settings to their defaults - Apple Support:- Return iPhone settings to their defaults
2. You can return settings to their defaults without erasing your content.
3. If you want to save your settings, back up your iPhone before returning them to their defaults. For example, if you’re trying to solve a problem but returning settings to their defaults doesn’t help, you might want to restore your previous settings from a backup.

If nothing above works probably it could be your iPhone may have a WiFi radio or antenna problem. In that case, take your device to an Apple Retail Store or Apple Authorized Service Provider, or contact Apple Support and get the hardware tested and if needed repaired/replaced.

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