Hey!
Why Dont you Backup all your data using Asus Backup app.
And Factory Reset your phone or Please CHECK IF YOUR TEMPERED GLASS/SCREEN PROTECTOR.Is causing problems.
If nothing works please replace your phone in flipkart!
Go To Settings> zen motion> tick double tap lock and double tap unlock. Gesture Controls Should be enabled to make it work.
Also, make sure you use an empty area of the screen to tap.
One additional thing you can do is to Check if other gestures are configured like Making C on locked screen for Camera etc...
As I have mentioned that all my settings are OK and it is a Brand New Device received yesterday so there is no requirement of Hard Rest/Factory Reset.
I think there is itself a bug and that is why ASUS have released this update. See the first point.
I have updated today to V1.12.40.349 but double tap to wake up still fails.