Two problems im having:

1. Essentials /sell conflicts with this one
2. /guishop sell 10 is refusing to work giving me this error:
   [13:34:15 ERROR]: null
   org.bukkit.command.CommandException: Unhandled exception executing command 'guishop' in plugin GUIShop v8.4
   at org.bukkit.command.PluginCommand.execute(PluginCommand.java:47) ~[patched_1.16.4.jar:git-Paper-416]
   at org.bukkit.command.SimpleCommandMap.dispatch(SimpleCommandMap.java:159) ~[patched_1.16.4.jar:git-Paper-416]
   at org.bukkit.craftbukkit.v1_16_R3.CraftServer.dispatchCommand(CraftServer.java:807) ~[patched_1.16.4.jar:git-Paper-416]
   at net.minecraft.server.v1_16_R3.PlayerConnection.handleCommand(PlayerConnection.java:2021) ~[patched_1.16.4.jar:git-Paper-416]
   at net.minecraft.server.v1_16_R3.PlayerConnection.c(PlayerConnection.java:1832) ~[patched_1.16.4.jar:git-Paper-416]
   at net.minecraft.server.v1_16_R3.PlayerConnection.a(PlayerConnection.java:1785) ~[patched_1.16.4.jar:git-Paper-416]
   at net.minecraft.server.v1_16_R3.PacketPlayInChat.a(PacketPlayInChat.java:47) ~[patched_1.16.4.jar:git-Paper-416]
   at net.minecraft.server.v1_16_R3.PacketPlayInChat.a(PacketPlayInChat.java:5) ~[patched_1.16.4.jar:git-Paper-416]
   at net.minecraft.server.v1_16_R3.PlayerConnectionUtils.lambda$ensureMainThread$1(PlayerConnectionUtils.java:23) ~[patched_1.16.4.jar:git-Paper-416]
   at net.minecraft.server.v1_16_R3.TickTask.run(SourceFile:18) ~[patched_1.16.4.jar:git-Paper-416]
   at net.minecraft.server.v1_16_R3.IAsyncTaskHandler.executeTask(IAsyncTaskHandler.java:136) ~[patched_1.16.4.jar:git-Paper-416]
   at net.minecraft.server.v1_16_R3.IAsyncTaskHandlerReentrant.executeTask(SourceFile:23) ~[patched_1.16.4.jar:git-Paper-416]
   at net.minecraft.server.v1_16_R3.IAsyncTaskHandler.executeNext(IAsyncTaskHandler.java:109) ~[patched_1.16.4.jar:git-Paper-416]
   at net.minecraft.server.v1_16_R3.MinecraftServer.bb(MinecraftServer.java:1132) ~[patched_1.16.4.jar:git-Paper-416]
   at net.minecraft.server.v1_16_R3.MinecraftServer.executeNext(MinecraftServer.java:1125) ~[patched_1.16.4.jar:git-Paper-416]
   at net.minecraft.server.v1_16_R3.IAsyncTaskHandler.awaitTasks(IAsyncTaskHandler.java:119) ~[patched_1.16.4.jar:git-Paper-416]
   at net.minecraft.server.v1_16_R3.MinecraftServer.sleepForTick(MinecraftServer.java:1086) ~[patched_1.16.4.jar:git-Paper-416]
   at net.minecraft.server.v1_16_R3.MinecraftServer.w(MinecraftServer.java:1000) ~[patched_1.16.4.jar:git-Paper-416]
   at net.minecraft.server.v1_16_R3.MinecraftServer.lambda$a$0(MinecraftServer.java:173) ~[patched_1.16.4.jar:git-Paper-416]
   at java.lang.Thread.run(Unknown Source) [?:1.8.0_281]
   Caused by: java.lang.NullPointerException
   at com.pablo67340.guishop.util.ItemUtil.setSell(ItemUtil.java:103) ~[?:?]
   at com.pablo67340.guishop.commands.GuishopCommand.onCommand(GuishopCommand.java:119) ~[?:?]
   at org.bukkit.command.PluginCommand.execute(PluginCommand.java:45) ~[patched_1.16.4.jar:git-Paper-416]
   ... 19 more
   ``

1. problem easy fix: there is a way to like parse commands to other plugins. lemme look this up.
   https://www.spigotmc.org/threads/essentialsx-overriding-other-plugins-commands.268951/
2. problem: i dont really know whats going on there, but next time just remove the "10" and it should work.
   If it doesnt, just answer to this comment and ill investigate in the code.

says for me to specify a value when i run guishop sell with the alias /gsell

then set the sell command to sum like playersell just for testing.
if that works u can look what aliases arent used yet and use them

then set the sell command to sum like playersell just for testing.
if that works u can look what aliases arent used yet and use them

so guishop playersell? (for bukkits commands.yml) - doesnt work

Didnt work

and/playersell doesnt work

could you please test on 1.16.4 to see if i have something misconfigured?

1. In your config.yml, you can rename the GUIShop sell command to anything of your choice. If /sell doesn't work for you, you can change it to something else. The odd part is, I am using Essentials currently on 1.16.5, and /sell doesn't mess with Essentials at all.

/guishop sell 10 is not how the command is intended to be used.

Depending on your config.yml, you set custom sell commands to open the sell GUI. Default is /sell.

All a user would type is /sell, which opens a blank chest. You drop the items inside and close it. This will attempt to sell the items in the GUI.

It works for me on 1.16.5 and 1.16.4 completely fine. With /gs sell 10 there is a abasic answer. I think that u just didnt put any item in the sell inventiry, or dont have any items to sell. Ill investigate in the code to see where the error is