The Samsung Galaxy S10 update in the United States seems to be locking some users out of their phones. If you're seeing this article and you haven't installed the latest Android 9 Pie June Security update, then delay it and do not install it under any circumstances.
There are several users reporting on Reddit that the Galaxy S10 phones in the US on Verizon and AT&T cannot be unlocked after the firmware is installed. The new update should have only tweaked the security parts of the firmware, but it seems like a bigger bug has developed instead.
This new Android 9 Pie update rolled out in the United States locks people out of their Galaxy S10 devices, and the only way to regain control over them will require a complete factory reset via Recovery Mode. If you don't know how to factory reset your Galaxy S10 device from the Recovery Mode, then you should check the info listed here.
There are other reports saying that the same bug is present on the bigger Galaxy S10+ models, too. In case you own a Galaxy S10 or Galaxy S10+ and you live in the United States, then we strongly recommend you not to update your phone in the next couple of weeks. If the notification update you're getting comprises the "June 2019 Security Patch" in its upgrade details, then you should deny its installation and wait for another future update instead.
The new "lock/ unlock not working" bug is not reversible, as Samsung has removed the possibility to unlock their devices via Find My Mobile service. The only solution you can try would be to factory reset the phone and lose all your important apps and other data stored by the system partition. Also, the Factory Reset can only be removed using the Recovery Mode of your Galaxy S10 / S10+ device.
If your Galaxy S10 device doesn't experience the "lock out" bug yet and you are running the latest bug, then try to remove all the lock codes from your device until a new update is rolled out in the next few weeks. We don't guarantee that this will prevent the Galaxy S10 "lock out" bug to appear on your device, but you can try to remove the locks from your device and force it to boot in normal mode.