Server setup

IllegalArgumentException: Name and ID cannot both be blank

What the log looks like

java\.lang\.IllegalArgumentException: Name and ID cannot both be blank
Uncaught exception in thread Profile Lookup Executor #\d+\s+java\.lang\.IllegalArgumentException: Name and ID cannot both be blank

How to fix it

  1. Check the stack trace lines below 'fillProfileProperties' to see the trigger: 'SkullBlockEntity' means a placed player head in the world is broken, while 'LoginListener' means player login verification is failing.
  2. Update Paper and any plugins that create fake profiles or skulls—especially Floodgate, Geyser, Citizens, SkinsRestorer, and leaderboard plugins—to the latest builds available for your Minecraft version.
  3. If 'SkullBlockEntity' appears in the log and console spam continues after updating plugins, find and break player skulls in loaded areas (such as spawn hubs or leaderboards) that were created with Bedrock players or blank NBT profile tags.
  4. If players are disconnected on join behind an offline-mode BungeeCord or Waterfall proxy, open 'paper.yml' (or 'config/paper-global.yml' on modern Paper) and set 'bungee-online-mode' / 'proxies.bungee-cord.online-mode' to 'false' so Paper stops querying Mojang's session servers for offline UUIDs.
LoadersServer
SeverityBreaks something
CategoryServer setup

Check your own log

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