markovo
We all know under display fingerprint sensors are not great, but ROG 3s is exceptionally bad. I mean it doesn't even work 90% of the time. For the other 10% it takes ages to unlock. I have tried all my fingers and positions. It works only if you place the finger on the exactly same position you set it in the first place and even then it takes 1-2 seconds to unlock. Thank god there is face unlock that works.
ROG 3 fingerprint sensor is worthless
The finger registration process is very important. If you don't register all the sides of your finger, then you will have much less chance of registering it.
Some suggest that you should register the same finger more than once as different fingers. This will yield better results in the beginning but with time it can be the other way around and this is because the scanner learns and improves over time. If you have scanned your finger three times as different fingers, then this data will go into the first finger scan that recognizes your finger.
As Danishblunt pointed out. If you register your finger when it was nice and soft, and then you start using strong chemicals to clean your home, then you might get small cracks in your fingerprint and it will no longer get recognized as easily until it has healed again.
I suggest you delete your fingerprints and redo the whole process.
