This apears to be what Fal and others here posting on this topic have missed...
That a genuine Christian can and does sin, sometimes perhaps even for a season of time, its that the real one will eventually repent/confess come back to God after conviction by HS, while "posing" christians will stay in their sin!
Not that we cannot sin, but that the real Christian will by their very nature, and HS conviction, will confess and come back to the Father!
That is what is meant by "not practicing sin"by the Apostle John, as that it refers to one can sin after being saved, sometimes a lot/ for awhile, but cannot stay stuck in that, as will be 'forced" by new nature to find way back to God and get restored again!