OPPO’s OTA servers for older models are occasionally offline. If you get "No updates available," move to Method 2.
If the OTA doesn't appear, you can download the firmware directly from OPPO's official channels. Visit the official OPPO Software Update Support Page . oppo f3 nougat 711 official update download fix
This is the safest method if your phone is still on stock Marshmallow. OPPO’s OTA servers for older models are occasionally
: Some users successfully triggered the Nougat update by using a VPN (like oppo f3 nougat 711 official update download fix