They would be overwatered, overfertilized, wrong lights, excessive nitrogen, bad environment. So much can halt flowering just as a lot can extend flowering. If it was pure landrace sativa with 17 week flowering time it's also going to be a harder strain to grow all round.
Gellatoseeds looks like it was formed last weekend and chucking pollen but they did deliver seeds and they germinated so have honoured the buyer seller agreement, when you sort out your problem try them again and guarantee you will find them a lot better than this round.