Plugin appears to be working (haven't tested with people in different worlds yet though) it is just constantly spitting out errors in the console.
Server Info
CraftBukkit version git-Spigot-140f654-b446cb5 (MC: 1.13.2) (Implementing API version 1.13.2-R0.1-SNAPSHOT)
java version "1.8.0_131"
Java(TM) SE Runtime Environment (build 1.8.0_131-b11)
Java HotSpot(TM) 64-Bit Server VM (build 25.131-b11, mixed mode)
Plugins (28): WorldEdit, Harbor, WorldGuard, ProtocolLib, Core, AdvancedPortals, tpa, VoidGenerator, PermissionsEx, ArvinLib, mcMMO, Vault, GWarp, DeathTax, Herochat, TheNewEconomy, Jobs, PerWorldInventory, HolographicDisplays, PlotSquared, Multiverse-Core, HoloPlots, CrazyAuctions, Multiverse-NetherPortals, GriefPrevention, MV-ChatAlias, CommandSigns, RandomTeleport
*edit: Using latest jar for Harbor
Error
[10:39:36 WARN]: [Harbor] Task #21 for Harbor v1.4.3 generated an exception java.lang.NullPointerException: null at techtoolbox.Harbor.ActionBarMessage.run(ActionBarMessage.java:9) ~[?:?] at org.bukkit.craftbukkit.v1_13_R2.scheduler.CraftTask.run(CraftTask.java:81) ~[spigot-1.13.2.jar:git-Spigot-140f654-b446cb5] at org.bukkit.craftbukkit.v1_13_R2.scheduler.CraftScheduler.mainThreadHeartbeat(CraftScheduler.java:391) [spigot-1.13.2.jar:git-Spigot-140f654-b446cb5] at net.minecraft.server.v1_13_R2.MinecraftServer.b(MinecraftServer.java:893) [spigot-1.13.2.jar:git-Spigot-140f654-b446cb5] at net.minecraft.server.v1_13_R2.DedicatedServer.b(DedicatedServer.java:417) [spigot-1.13.2.jar:git-Spigot-140f654-b446cb5] at net.minecraft.server.v1_13_R2.MinecraftServer.a(MinecraftServer.java:835) [spigot-1.13.2.jar:git-Spigot-140f654-b446cb5] at net.minecraft.server.v1_13_R2.MinecraftServer.run(MinecraftServer.java:733) [spigot-1.13.2.jar:git-Spigot-140f654-b446cb5] at java.lang.Thread.run(Thread.java:748) [?:1.8.0_131]