While this is the most common method, OPPO has hidden Fastboot behind a specific timing . Simply holding the buttons won't work. Follow this exact sequence:
Select your language (e.g., English) using the volume keys to navigate and power to select. Look for an option titled "Reboot to Bootloader" "Enter Fastboot" . This will restart the phone directly into Fastboot mode. Important Considerations Fastboot Mode OPPO F1s A1601 - HardReset.info How to Open Fastboot Mode on OPPO F1s A1601
Sometimes the direct hardware shortcut may vary by regional firmware. An alternative method is to go through the Recovery Mode Power off and hold Volume Down + Power While this is the most common method, OPPO
If you still cannot access Fastboot after trying all three methods, your device likely has a carrier-locked bootloader or an updated ColorOS version that blocks the feature. In that scenario, consider using SP Flash Tool as a last resort or consult an OPPO service center. Look for an option titled "Reboot to Bootloader"
Since Fastboot is crippled on the A1601, use MediaTek’s native Download Mode for firmware operations: