If you mean this plugin by a forum member, it's 32-bit only and won't work with 64-bit versions of Opus. Most machines are 64-bit these days, so that is probably the problem.
If you can find a CSV preview handler, that should work in Opus, as well as in Outlook and File Explorer. But I am not sure one exists, or at least could only find other people looking for one from a quick search. You would think the Excel preview handler could handle CSV files but it can't; only xls and xlsx files, for some reason.