Help desk technician interviews are designed to test your ability to communicate clearly and solve problems over the phone to people who are often flustered. Good communication and the ability to simplify solutions are key qualities for potential employees. Certain certifications may be required depending on the field of work.
How would you troubleshoot a problem connecting to a network resource.
There are several questions to ask the customer starting with 'when was the last time you could access this resource? what has changed since then? I would also trying pinging the IP address or perhaps doing an nslookup to see if it might be DNS related problem etc...