Error: "No Domain" after having selected Site2 domain database and started merge

Error "No Domain" after having selecting Site2 domain database and started merge.  Packet trace of workstation shows domain database is being read without problem. 

 

The external domains created to link Site1 and Site2 needs to be named identical to the domains they link to.  For example if Site2 domain is called "domainb", then the external domain created in Site1 needs to also be named "domainb"