I am sorry to say but you shouldn't bother. I had the same problem with my first vox (actually 2nd as the first had to go back within 2 days) back in June after about 6 months use. Kobo couldn't do anything about it so I had to send it off to the netherlands (at a cost of £50 to myself). They replaced it with a new one. Yesterday the same thing happened. I now have a piece of useless plastic with a flashing green light! Kobo talked me through all the usual things nothing worked. I told them I wanted my money back - which they have refused (I did point out the terms of the sales of good act!). They want to replace it - but I am not prepared to spend another £50 to send it back.
I suggest you try to insist on getting your money back, regardless of its age. Once you have got to this stage it will never restart.
My advice to anyone out there, do as I did today and go look at the many alternative 7in android tablets on the market from manufacturers that produce goods that work!