by Helena Bundock.
Hi don't know if you ever resolved this but I had the same issue.
I didn't see this in any of the documentation I did some test uploads and found I had to add a cohort ID to the cohort and then it would recognise the cohort when I uploaded.
The other thing I had to do if the users already existed (from previous test uploads) was to choose to update existing users and then it went through and assigned the user accounts to the cohorts.
Cheers
Helena