Legrand USB Outlet (USB socket dead after minimal use)
Unfortunately these USB sockets fail regularly. We constantly seem to be replacing them. The irritating thing is that the failures aren't all from crap brands. Market leading brands like MK and Legrand fail just as much as the cheap china knock offs. I have never seen any of these sockets to be fused before. But, clearly they are overloading. iPads and other tablets seem to be the largest culprit as they draw way more than standard current. However, It's a disappointment from the mainstream brands that they do not have a self resetting overload function or at a basic level a simple fuse. Crazy how smaller electronics companies can make robust chargers yet they cant.

As for diagnosing. There really inst anything to diagnose unless you try a different cable and device to check for charging. Normally it will require replacement. I would ask though what are you charging in this device. And secondly do you have the socket part number as the socket will have a data sheet with its maximum rated current for the USB socket part.