When you run /vanish fakequit or /vanish fakejoin, it gives the error access denied.

http://dev.bukkit.org/projects/vanish/pages/permissions Make sure you’ve given yourself the correct permissions

Well, I have all the permissions, I am the operator @Dinty1.

No I am not using a permission plugin, I have Geyser, VanishNoPacket. Floodgate, DiscordSRV, ViaVersion, GriefPrevention, ProtocolLib, LoginSecurity, Openinv And PluginHider lastly.

Are you using a permission plugin?

VanishNoPacket doesn't grant literally every permission node to ops.

Grab yourself LuckPerms and grant the permission nodes you want yourself to have according to the documentation! 😄