"There is a seniority list in Norwegian, we are on it"
Norwegian has no obligation to follow any seniority list with respect to contractors. The agency employment contract does not contain a seniority clause with the lessee airline, Norwegian.
Irrespective of your eligibility and any training payment, as a contractor you have no recourse whatsoever should Norwegian not offer you the opportunity to upgrade.
If you are looking for something to work out, try working out the length of a Kjos "transitional period", after which you are offered direct employment with a company in the Norwegian Group - ref Kjos letter to DoT, June 1, 2015.