Type /ver NametagEdit and post the output.
4.4.0

What version of Bukkit/Spigot/PaperSpigot are you using? Type /ver
1.13.2 paper

Sometimes the tablist will just not show a prefix even on reboot. Debug shows nothing.

Same problem
PaperSpigot 1.12.2
https://i.imgur.com/sMtMZsg.jpg