User: "There's no Ethernet connections at these four desks"
Me: "No problem, on my way"
*checks desks, all showing Ethernet disconnected*
Me: "Hmmm."
*checks comms room, no activity lights on any of the ports on the switch*
Me: "Ahhh."

FTR this switch has 30 devices plugged into it and none of them are active. Affected users devices have all fallen back to WiFi so most are unaware of the fault.
Time to get the networks team involved.

As suspected the switch had fallen over. Local restart (pulling and reseating the power cables) fixed the fault!

This has reminded me that I should put an Ethernet cable tester into my work tool bag.

Also I'd love to get artwork of myself working in a comms room, maybe arms deep in a mass of cat6, lol