Depending on the initial version of Vista it may be necessary to order and use the "Upg" licenses when upgrading from an older version of Vista to the current version
TAC Vista versions within the same sub range:
License upgrade types
The licenses are limited to the ranges of 5.0.x and 5.1.x. Upgrades within these ranges are free.
5.0.1 to 5.0.3 is free of charge.
5.0.1 to 5.1.0 needs upgraded licenses. Use the "Upg" license package when ordering.
5.1.0 to 5.1.5 is free of charge.