How best should I be using these workouts, I didn’t complete the first one so should I keep trying until I do complete each section or keep moving to the next day?
I think your answer depends largely on this: Why didn’t you complete the first workout?
If the answer is “because it was too hard and I couldn’t complete all of the intervals as prescribed.” - then you probably have your FTP set too high to begin with.
Have you taken an FTP test before starting? Or are you just using the default setting? With any FTP builder series, it’s important to have a good handle on what your FTP actually *is* going into it.
If, otoh, you’re just not feeling 100% one day and you have to skip 1 block toward the end, I’d progress to the next workout in the series without bothering to repeat… but on Week 1, Day 1? IDK… it should be manageable.
Thanks for the reply. I had done FTP test and came up with 189w, since then on my profile it shows that over 20mins best was 199w so I had changed it.
So I hopping its because I wasn’t 100%, I will do the test again and go from there.
PS, loving Zwift guys 
The way FTP is calculated is taking 95% of your 20min best. So an FTP of 189W will come up as having a 20 minute best of 199W on the critical curve on your profile. If you changed your FTP to 199W then you will be starting the workout with a FTP 10W higher than you can cope with and could be the reason for you failing the workout.
Makes Sense thank for explaining it.
@Ray - thanks for the explanation on how FTP is calculated! I wondered why my FTP was set lower than my 20 minute best.