I'm talking from memory here, I will have to investigate to be 100% sure.
DiceBot does not hanlde references for the LUA environment, LUA handles it itself. The version of LUA used in the bot is fairly old (it's not trivial to update to the newest version, otherwise I would have by now). It's very possible that the version of LUA of that specific lua library does not support the functionality that you're trying to use.
Edit: The problem is your csv file. the lua environment checks various folders and it finds your file.
Read your error message: Could not load file or assembly 'file:///C:\Programs\DiceBot 3.3.22\csv.dll' or one of its dependencies. The module was expected to contain an assembly manifest.
It finds your file, but the file is not valid. It's not a DLL but has a DLL extension.
If the bot could not find the file, it would say:
module 'csv' not found:
no field package.preload['csv']
no file '.\csv.dll'
.
.
.
etc
Again, this might work in your other lua environment and not in DiceBot because DiceBot is using an older version of LUA. It might even just be a different implementation of LUA and does not have anything to do with the version.