Many reasons why a order gets cancelled from any given shop they'll go through risk assessment system which will take into consideration several variables, it really depends on the shop and country and what's getting you flagged, it's no surprised if you've been following what most people tell you what to do in tutorials you're just gonna get flagged, it's not about a 'method' there are things that it's just about infrastructure and geolocation shenanigans that will get you flagged, wrong locate timezone things like that even can get you flagged.