Could not find server 'server name' in sys.servers. SQL Server 2014

At first check out that your linked server is in the list by this query

select name from sys.servers

If it not exists then try to add to the linked server

EXEC sp_addlinkedserver @server = 'SERVER_NAME' --or may be server ip address

After that login to that linked server by

EXEC sp_addlinkedsrvlogin 'SERVER_NAME'
                         ,'false'
                         ,NULL
                         ,'USER_NAME'
                         ,'PASSWORD'

Then you can do whatever you want ,treat it like your local server

exec [SERVER_NAME].[DATABASE_NAME].dbo.SP_NAME @sample_parameter

Finally you can drop that server from linked server list by

sp_dropserver 'SERVER_NAME', 'droplogins'

If it will help you then please upvote.