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.