Select your device model (OPPO F19s) from the list of available devices.
Get the Oppo F19s CPH2223 Stock ROM package and extract it on your computer. oppo f19s flash file repairmymobile install
Flashing the firmware manually may void your warranty if the device is still covered. If the device is new and stuck, consider visiting an authorized Oppo service center. Select your device model (OPPO F19s) from the