CSV Upload Error

I've been having a repeated issue with attempting to add to my inventory via the CSV upload. I have used this method dozens of times and I've encountered the typical error of a set name being formatted wrong or whatever, those are normal and fine. But this is new and happens no matter what I've tried. I reached out to support and have not gotten an answer yet.

Error: The server encountered a problem trying to import your file. Please check that it is a plaintext csv file and try again. Extra information: undefined local variable or method `msg' for #<ActionView::Base:0x0000000285a578>