Done all that and no I've not added anything other than ammonia.
I had the same result the test went light green not one of the colours on the card

i thought maybe the nitrite had spiked and so i done a 90% water change thinking i may be getting some fish after this i thought i would just check to make sure all was well and the nitite was deep purple (over 5ppm)

i emailed API via thier contact page but they have not replied so i am now carrying on feeding amonia daily and the nitrite is still at or over 5ppm with no nitrates over a week later, i was thinking about doing another 90% water change to see if it has the same affect on the nitrates as it did on the nitrite

maybe these silly bacteria are stuck in the gravel and just need a good stirring up to get then moving