why sp_ExecuteSql output parameter returns null from linked server when procedure shows correct value in results panel

I am trying to get SQL version from a linked server and save it in a variable, but the query runs fine and showed me the result but when I review the output variable is Null. DECLARE @cmd NVARCHAR(MAX); DECLARE @servername NVARCHAR(MAX); DECLARE @result NVARCHAR(500); SET @servername = 'SERVERNAME'; SET @cmd = 'SELECT * FROM OPENQUERY([' + @servername + '], ''SELECT @@VERSION'')'; EXEC sp_executesql @cmd, N'@queryresult NVARCHAR(500) OUT', @result OUT; SELECT @result;