I am currently having an issue where any player that is not opped cannot use the /nickname command

It shows up as such -

However the permission to use it is set

Hm. I've not seen this before.

Can you provide the contents of your config/EssentialCommands.properties and a https://mclo.gs/ (or equivalent) of your logs/latest.log?

The logs just say
[17:30:56] [Render thread/INFO]: [System] [CHAT] Unknown or incomplete command, see below for error
[17:30:56] [Render thread/INFO]: [System] [CHAT] nickname test<--[HERE]

heres the config https://mclo.gs/h7A7ZUe

You have use_permissions_api set to false in your Essential Commands config. Changing it to true will likely solve the issue ;)

This was the case! Thank you