My WiFi is blocked and I don’t know why?
Reset Network Settings: Only network settings are removed.
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.
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.
Find Locations - Location Selector - Apple
Contact Apple for support and service - Apple Support
Get a Genius Bar Reservation and Apple Support Options - Apple
Contact Genius Bar. Manage Reservations - My Reservations - Apple