Some devices connected to a usb-c hub sometimes do not show up

I have a Lenovo Yoga C940 laptop, which has USB-C ports that I connect to a Dell USB-C hub when I am at my desk. The hub has a disk drive, an HDMI monitor, a soundbar, and a webcam conneccted to it. Sometimes, not all the devices connected to the hub show up when I plug the hub in, most commonly the disk or the monitor. Sometimes the hub does not provide power for my laptop. As far as I can tell something is preventing these devices from being recognized or preventing power from being set up.

I realize that there could be lots of reasons for these problems, so I’m only asking whether there is something that I can do to see more information about the attempted connection or the state of my laptop before the connection so that I can try to narrow down the problem.

It sounds like you are likely drawing more power from the USB port than it is capable of outputting. You might need to find need to find a different power source for disk drive, in particular.

The hub is a Dell WD15 which appears to have at least 130 watts of power available from its dedicated power transformer. As my laptop should only be drawing at most 65 watts of power that leaves a lot of power. With only three USB-connected devices the maximum draw there is under 20 watts. The monitor should not be drawing significant power. The hub itself will draw some power but there is over 40 watts still available, which should be much more than needed.