Hello, I'm sorry in advance if this question was to be discussed with the developer of EssentialsX but I also have another issue regarding that.
So I watched the tutorial on how to set and customise ranks (below). Part of it included editing the config (7:02). I followed their instructions, definitely pressed the save button, and it worked. I also edited some other things in the config, and saved, which worked perfectly fine.
However when I logged out and logged back in, everything I edited from the config file changed back to default. My gamemode, which was previously creative, also changed back to adventure, which I set as the gamemode of the server. These things happen everytime I log out and back in to my server. Please help!!