Troubleshooting Lexicon Event Import Issues in New Project Setup

Hi team, I'm setting up a brand new project. I'd like to import event definitions into the Lexicon. I'm using the exact format a described here, based on a lexicon export: https://docs.mixpanel.com/docs/data-governance/lexicon#csv-import. the file is saved in UTF-8 format. i get as far as selecting the file and the Next button is x-ed out. i'm a billing admin on the account and an admin of the project (though not the owner) so i think i have enough privileges. any help would be appreciated. (i've been all over the docs, slack, bot channels.) seems like a file format issue but missing the obvious somehow. thx.