1.15+ Villager professions are no longer valid.

[Chaoswizard98]

Back in 1.15, Mojang changed how villager professions are handled. They are no longer a number, but a string value such as farmer, shepherd, stonemason, etc.

Shop inventories still work the same, it's just the career level and profession variables that no longer work and result in the creation of a jobless un-trade-able villager.

The version I'm using is the current 1.16 version.