Sofosbuvir/Daclatasvir (which is what's in Darvoni) can be taken with or without food so don't beat yourself up about that - it would not have made any difference.
The sad reality of anything less than a 100% success rate is that X% of people fail, regardless of the treatment or the manufacturer.
Retreatment is complicated. There is an entire section on the forum dedicated to it and I'm summarising all of that in a series of blog articles. Here is part 1.
What I would suggest is that you make an online appointment with me and we can work out a plan. In the event you do get access to Mavyret you should strongly consider adding Sofosbuvir to it, or you should chase Vosevii via insurance.
You can find me online by registering at gp2u.com.au/
and booking one of my "Hep C Only" appointments.