"Login Attempts To Lock User" is a GAM Repository property used to specify the number of login failures until the user is locked.
The GAMRepositoryConfiguration web panel (located in GAM Example folder) is an example where this property is used.
The way to use it in GeneXus code (by using the GAM API) is the following:
&Repository.LoginAttemptsToLockUser = &LoginAttemptsToLockUser
When blocked, the user needs to be un-blocked by the Administrator of GAM Backoffice. In GAMExampleEntryUser, uncheck the "User is blocked" property, as shown in the following figure:

Figure 1. GAMExampleEntryUser form.
See GAM Unblock User Timeout property as another way to unblock user sessions.
Login attempts to lock session Repository property
GAM Unblock User Timeout property
GAM Repository features and properties