Ensure your OPPO A17 has at least 50% battery. If the phone dies during the reset, you could corrupt the operating system.
Inside Additional Settings, find the option that says "Back Up and Reset" or simply "Reset Phone." How to Hard Reset OPPO A17
Physical damage or stuck keys. Fix: If the volume buttons are broken, you cannot navigate recovery mode. You must use the Settings method (if you can unlock) or take it to a service center. Ensure your OPPO A17 has at least 50% battery
– What if the OPPO A17 doesn’t enter Recovery Mode? The guide should suggest: How to Hard Reset OPPO A17
– Mentioning the OPPO logo and “No command” screen with the solution (press Power once, then tap Volume Up) is a lifesaver for beginners.