All the way back in Android 5.0 Lollipop, Google added a 'Trusted Face' mode to Smart Unlock, giving all devices a slightly-secure way of unlocking with the front camera (the easily-fooled face unlock in Android 4.0 doesn't count). However, many people on the latest Android Q beta are having issues with it. If you're in that group, don't worry, there's a fix you can try.

There are already dozens of reports across Reddit and other sites of Trusted Face mode not working, even after disabling and re-enabling it again from the Settings app. Some even speculated that Google was removing the existing face unlock method to prepare for the Pixel 4's more advanced equivalent. However, the apparent removal seems to be nothing more than a bug.

Reddit user MawMaw2864 found a way to fix it, which involves going into the Developer Options in the Settings app and toggling 'Trust Agents only extend unlock' off and on again:

I had issues with Trusted Face on Beta 6 like others, and I think I found a fix I wanted to share. Settings > System > Advanced > Developer Options > Toggle on "Trust Agents Only Extend Unlock > Toggle it back off > Profit

If you don't already have Developer Options enabled, just find where the 'Build number' is listed in the Settings app (on Pixels, it's under 'About phone') and keep tapping it until you see a confirmation message. However, trusted Face mode is still unavailable to the Pixel 3 and 3 XL.

Thanks: Keanu Kerr