I'm playing on the most recent 1.18 version.

After buying the +1 enchantment level power, the first enchantment I did worked correctly and gave me Protection V, etc.
However, subsequent enchantments have not received the extra level.
Reloading the game did not fix it.

Update: After playing some more, the effect seems to only work some of the time. When I do a bunch of enchantments in a row, it sometimes only activates for a couple and sometimes works for all of them. When it doesn't work, the enchantment also isn't giving me xp towards the enchanter job.