How do I turn the knockon feature back on?

• Phone model: LG-H850
• Hardware version: Rev 1.0
• Android version: 8.0.0
• Build number: OPR1.170623.032
• Software version: V30f-EUR-XX

For those of you who don’t know - LG phones come with a feature called knock on, which allows you to double-tap on the screen to turn the screen off, and double tap again to turn it back on. I’ve always been an avid user of this feature as the power button is situated on the back of the phone, so it’s a convenient feature for when the phone is flat on a surface.

Some time ago, the feature stopped working entirely. I can’t pinpoint an exact moment or update when this happened. Since I’ve noticed the feature being disabled, I’ve tried the following things:

• Checked for software updates for both apps and android. None are available.
• Uninstalled all recently installed apps.
• Tested the touch screen to make sure it wasn’t just an issue with me tapping a broken part. Touch screen works perfectly.
• Tested the proximity sensor to see if it was an issue with that. Proximity sensor is working perfectly.
• Installed various “hidden setting” apps to access the knock on feature. Unfortunately the knock on feature is never available in the list, which is strange. It’s almost like the entire feature vanished from my phone overnight.
• Installed different launchers as some youtube videos recommended this, to no avail.
• I have not yet done a factory reset, and would like to avoid this if at all possible, but if someone has reason to believe this will fix the issue at hand, please let me know.

Could anyone recommend how to fix this issue, regardless of whether it’s a software or hardware fix? I’m totally comfortable with taking the phone apart if need be, but if I can solve it with a settings tweak that would of course be preferable.

Thank you in advance!