Survey Branching on Embedded Data

I'm trying to create a closed sample survey with a version A and B that branch mid-survey based on predetermined groups. I created an email distribution list with an additional column in the file for "Path" to determine whether the respondent's personalized link branches them to version A or B of the survey. When I try to pull this into the survey flow following the instructions on the FAQ page, I'm able to add embedded data and find the "Path" variable, but the dropdown for choosing an entity (i.e. version A vs. B) is empty. Can someone who has set up predetermined survey paths/branching based on a variable in the respondent file advise on how to properly set up embedded data and use it in survey flow?