FST - Not able to sync users

Hello, 

I've connected a new instance to FST and am having trouble syncing users to the application.

In the CRM error logs, I am receiving this error for all users:

Something wrong with user data. You need to send non-empty first and last name, valid email address and licence type

I've confirmed that all my users have a valid first name, last name, email address (they are able to receive emails) and either an Enterprise or Professional license.

Any insight would be appreciated.