You run the Host Integration Server 2016 Migration Tool against a Host Integration Server 2013 system. If the system is a nodeless server, the migration tool does not recognize the name of the primary server.
This problem is fixed in Cumulative Update 1 for Host Integration Server 2016.
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.
Learn about the terminology Microsoft uses to describe software updates.