A little late, but here is what I usually do when a ticket like that comes in:
Check monitoring. It’s quick and easy to check so I’ll look before even asking any clarifying questions. If there is a real network problem at a site, 95% of the time its going to show up on our monitoring dashboard. Everything from ISP outages to device failures show up here.
Ask for more details about what they are trying to do. What is the goal? What are you doing? What is happening? What should be happening? When was the last time it worked?
Based on those details, I can usually put together a good guess as to what might be going on, so i’ll test that theory out and see if i’m right.