I ran into this same issue with an 'Autoflower'. I was patient and at week 12 I still saw not signs of flowers forming. I treated it like a photoperiod and switched to 12/12 light schedule to get it to flower. In the future if I should run into this I will not let it go past week 6 before treating the plant as a photoperiod. It is my understanding that autoflowers should start to show flowers forming between weeks 3 and 5.