I am also facing this issue from the last update of android pie
I am having an issue using the "Lift To Wake" feature on my AT&T Galaxy Note 9 phone! I have gone into my phone settings and selected the "Lift To Wake" featurs, making sure that it is turned on (which it is). However when I have my phone laying down on a flat surface (tried both front side down, and back side down), when I go to pick up my phone nothing happens! Im pretty sure that with the "Lift To Wake" feature turned on, it should wake up immediately or at least shortly after you pick the phone up. Below are some basic troubleshooting ideas that I've already tried out!
1.) Turned "lift to wake" feature off and then on.
2.) Reset the phone after switching the "lift to wake" feature on.
3.) With the "lift to wake" feature turned on, I've tried getting it to work with my phone case on and off, and both laying frontside and or backside down on a flat surface.
4.) Tried powering off the phone after the "lift to wake" feature was turned on, and waited 30 seconds before powering up my phone.
5.) Tested out many different ways that someone might pick up a phone after it was laying down on a flat surface.
The things above are all ideas I've tried out. Unfortunately though, none of these things got the "lift to wake" feature to work as expected on my phone ?! The only other Idea I've had but have not yet tested, is to see whether the "Pop Socket" that I have stuck on nearly dead center of the backside of my phone, might be a possible contributing factor to this phone issue. I've also attempted googling this particular issue with many different search phrases, and after nearly an hour of searching, found nobody on the internet who has experienced this issue themselves, and found no solutions or even advice over this matter! I'm at a loss of what to do! I'd love to be able to use this convenient feature, and if I just can't seem to get this feature to work than so be it ?! So any tips, advice, troubleshooting methods and or solutions that you guys have, I'd love to hear them, and it would be much appreciated! Cheers everyone ?!!