This is available only through an VLA or Annual VLA. If you purchased just one copy of FMPA you will pay the upgrade price in the FileMaker store page. If you want to move into a VLA you need to purchase 5x FMP(A) or at least 1x FMS to receive the VLA pricing.
Sounds like the marketing materials may have left out the minimums or maybe you missed it.
Thanks for the info.