To clarify: autoflowers are not nearly as locked into their flowering timeline as breeders may have you believe. Most begin showing sex around weeks 3 to 7, but genetics, transplant shock, root restriction, environmental stress, and other early setbacks can all delay the transition from vegetative growth to flowering.
I noticed you transplanted this plant twice, which may have contributed as well.
At six weeks, I'd still give it another 1 to 2 weeks under its current conditions and keep an eye on the upper nodes for pistil development. If there's still no sign of flowering after that, or sooner if you want to rule out a genetic abnormality, you can switch it to a 12/12 light cycle. If it turns out to be a true autoflower, reducing the light cycle will likely cost you some yield, which is why I'd wait before making that change.
One other possibility is that this seed simply didn't inherit a fully stabilized autoflower phenotype. The autoflower trait comes from Cannabis ruderalis genetics, and if a breeding line isn't completely stabilized, you can occasionally end up with offspring that behave more like photoperiod plants. It's uncommon with reputable breeders, but it does happen. In the same way that a very small number of "feminized" seeds can still produce males, a similarly rare exception can occur with "autoflower" seeds.