Odin mode Key Combo erased after flashing

Is there any file or program that will flash the Download Mode ''key combo (Vol-, Home, Power) back'' onto my phone?

I'm very well immersed in Android modding/rooting, especially Samsung devices, but never have I once not been able to boot to Download Mode with the key combo (Vol -, Power, Home). After reflashing stock firmware, I am now unable to boot to Dwnld Mode with the key combo. ADB & terminal commands work fine but the key combo literally will not work. It simply reboots my device like a normal boot up.

My phone isnt damaged physically, so that's not the issue. adb reboot download & reboot download with root access both boot into Dwnld Mode just fine. Key combo has somehow been eradicated.