NFI has the tendancy of going very bad with payables for a long period of time. I remember this back in 2010-2013, the were awful and always blamed changes in their accounting depatment. I can just recommend trying to contact their US operation, maybe that will fetch you somehting.
Last invoice we had with them wasnt being paid after 40 days, we got the broker that gave us the load involved. Thats also a good option, they can usually tell you whats going on with accounting. If you need help PM me and I will give you the email I have used.