do I need to put the plant back to veg then to flower again? if so how long? was it too young to flower?
Hiya serrated
Your plant isn't sexually mature enough to have been put into flowering and this will increase the amount of time it can take for sex to show. The less time you veg the plant for the longer it can take to show sex during flowering. Now you've switched the plant into flowering it would be silly to switch back to vegetative growth because that will confuse and stress the plant - you have to continue in 12/12. Here's a few tips to ensure your plant starts to flower -
1) Make sure there are NO light leaks in your flowering chamber. Any light leaks, even small ones can stop the plant from entering flowering stage - this is even more important with yours due to it's immaturity.
2) Make sure your light source is predominantly a red spectrum one. The pigments in the plants chloroplasts that act as the plants 'internal clock' that tells it when the day length is shorter and it's time to start flowering is highly reactive to red spectrum light - that's why flowering is induced faster with predominantly red spectrum light sources such as HPS's.
3) You could try forcing the plant to enter flowering by giving it double or triple the usual dark period. ie if your on a 12/12 schedule, try giving the plant 24 or 36 hours of darkness and then back onto 12 hours of light 12 hours of darkness schedule. This will effectively 'reset' the phytochrome pigment that reacts to the red spectrum light, but this will have no affect if there are any light leaks in your flowering chamber, so sort those out first before trying this.