Hi, this is a known bug, let me briefly explain:
There is an experimental feature in Anti-Theft (not visible in the Settings), which keeps an eye out for SMS commands with a wrong PIN. Unfortunately this feature is a bit too “sensitive” and from its point of view any SMS with a string of numbers is assessed as an invalid command.
Moreover, out of some reason this feature is connected to the “PIN Security”, so if it is on and you get 8 SMS messages evaluated by Anti-Theft as invalid commands, the device gets locked. And as there is no time limitation, so the 8 invalid commands can be piling up for months.
There is a workaround - you can disable the “PIN Security” feature:
- open Avast Anti-Theft by “calling” your Avast PIN
- tap on the three-dots icon in the upper right corner
- select “Settings” in the menu
- turn the “PIN Security” off
Colleagues have already been working on a fix and this bug will not be present as of the upcoming version.