Sql Server Replication requires the actual server name to make a connection to the server

I get the following message when I want to create a Remote Distributor. First i delete my whole configuration of replication then after i take a first step to create new replication and i get below error for creating a Distributor....

I already do this but still same error........

sp_dropserver 'NODE-XYZ';
GO
sp_addserver 'NODE-XYZ', local;
GO

when run this command to get actual name then i get 'NULL' value

SELECT @@SERVERNAME
GO