Make sure the phone is fully turned off before plugging it in. If it still fails, hold both volume buttons together while plugging in the USB cable.
Eliminates deeply rooted viruses and frequent system crashes. Oppo F1s Mt6755 Firmware
Windows needs specific drivers to communicate with the MediaTek MT6755 chipset while the phone is powered off. Download and install the MTK VCOM Drivers or All-in-One MediaTek Drivers. 3. SP Flash Tool (Smart Phone Flash Tool) Make sure the phone is fully turned off
from the firmware folder, selecting the "Firmware Upgrade" or "Download Only" mode, and connecting the device while holding the China Miracle M2 (CM2): Oppo F1s Mt6755 Firmware