In the economy page, do you have the salary floor value in red? I was at 400k salary on Monday and our floor is 420k, I obviously paid 420k since I'm way past the 16 weeks moratorium, however I noticed that my floor was highlighted in red.
Check your economy page to see what you actually paid on Monday the 15th in salaries; although you are not a new team, the salary floor that should have applied (if any does this week, which I don't believe it did) would have been the one from last season. I know my salaries at the time of the rollover were only 87997 and my new league floor is $116884, but I was not assessed that amount (my old league had a lower floor).
If you actually paid the $420k I would consider that as a bug. If not, no harm no foul.