Samsung's new fingerprint sensor uses ultrasound rather than optical scanning. The sensor works well overall, but with a thick bulletproof glass over the display it obviously has problems and no longer recognizes the fingerprint.
According to Samsung's statement:
"To ensure the full functionality of the ultrasonic fingerprint sensor in the Galaxy S10 and Galaxy S10+, Samsung strongly recommends that our suppliers and resellers only offer Samsung display protection films as accessories. We cannot guarantee our experience with display protection films made of traditional glass and polyurethane materials."
In other words, the fingerprint sensor in the Galaxy S10 and Galaxy S10+ is unlikely to work with other than Samsung films. This is exactly what the first testers of the new Galaxy smartphones report.
Luckily, Samsung will supply a detachable screen protector for the Galaxy S10 variants with ultrasonic sensors right out of the box. Naturally, the company recommends you stick with this one, or its own $29.99 dollar replacements. The pre-installed screen protectors are covered by 90 days warranty.
The Galaxy S10 has a problem with glass display protection
The behavior of the Galaxy S10+ can also be seen in the video by Marques Brownlee. The prominent YouTuber tests the fingerprint sensor both without screen protector and with a film and a glass screen protector, and lo and behold: once you put glass on the display, the smartphone can no longer be unlocked. The corresponding part of the video starts at 6:45 minutes, if you don't want to watch the complete video.
This is bad news for all those who want to protect their expensive smartphone from scratches or cracks with bulletproof glass and similar display protection materials. As a biometric unlock option, only face recognition is available - and only in 2D. Samsung has deleted the iris scanner from the Galaxy S10 and Galaxy S10+ without replacement.
By the way: The cheaper Galaxy S10e doesn't have this issue, because here the fingerprint sensor is in the powerbutton at the side.
Do you use 3rd party screen protectors on your device?