I know there is currently no 1.13 support for NametagEdit, but I found this issue:

Bug Report

Type /ver NametagEdit and post the output.
[19:42:55 INFO]: NametagEdit version 4.2.0
[19:42:55 INFO]: Authors: sgtcaze and Cory

What version of Bukkit/Spigot/PaperSpigot are you using? Type /ver
[19:43:26 INFO]: This server is running Paper version git-Paper-45 (MC: 1.13) (Implementing API version 1.13-R0.1-SNAPSHOT)
[19:43:26 INFO]: Checking version, please wait...
[19:43:26 INFO]: You are 3 version(s) behind

19:53:51 [INFO] This server is running BungeeCord version git:BungeeCord-Bootstrap:1.13-SNAPSHOT:6fadb42:1343 by md_5

What plugins are you using? Type /plugins
[19:44:02 INFO]: Plugins (2): GroupManager*, NametagEdit*

Please explain your issue. How do you trigger it?

• Running NametagEdit behind Waterfall/BungeeCord on a Spigot/Paper 1.13 Server nobody can login.

Running NametagEdit without Waterfall/BungeeCord works fine on 1.13.
Also running NametagEdit on 1.12.2 Spigot/Paper works fine behind Waterfall/BungeeCord.

Are there any errors in the console? Please use: https://pastebin.com
https://pastebin.com/hC7pEerR

Closing and refer to #298