Sounds about right! I plugged my Mega2560 R3 Clone into my laptop and that’s what mine does as well. I would say that the board is ok based on that. You only get TX and RX when the USART is working/in use. After a reboot, the Arduino Language/System disconnects the RX and TX pins and disables the USART. Those two pins become D0 (RX) and D1 (TX) on an Uno, but are RX0 and TX0 on a Mega 2560 R3 as that little beauty has three Serial interfaces. (Apologies if Grandma already knows how to suck eggs!)
Covid is an effing nightmare. Apologies for language. I can cope with it most of the time, being a “hermit” (or so my wife says!) but she’s a sociable person and it’s driving her nuts. I think it will be quite a while before we are “normal” again.
I mentioned running
dmesg --follow i=on a Linux device. This is what my laptop reports:
[ 878.680035] usb 5-2: new full-speed USB device number 3 using uhci_hcd
[ 878.900114] usb 5-2: New USB device found, idVendor=2341, idProduct=0042
[ 878.900118] usb 5-2: New USB device strings: Mfr=1, Product=2, SerialNumber=220
[ 878.900121] usb 5-2: Manufacturer: Arduino (www.arduino.cc)
[ 878.900123] usb 5-2: SerialNumber: 85535303536351E04032
[ 878.902218] cdc_acm 5-2:1.0: ttyACM0: USB ACM device
I suspect it’s not a genuine Arduino, regardless, but I can see that plugging it in has registered in the system. Unfortunately, I’m not able to tell you how to do this on Windows. Unless USBDVIEW helps? http://www.nirsoft.net/utils/usb_devices_view.html - I assume your student has privileges etc to install software?
Alternatively, can she access the registry? HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\DeviceClasses is apperently the place to go. I would look that up before plugging in the board and see what/how many entries there are. After plugging in the board, F5 (I think) to refresh and see if anything comes up.
If so, I would suspect a missing driver for the comms chip on board the Mega 2560, if not, 99% certain it’s the cable. (Or, a duff comms chip!)
Not by looking at it - unless it’s transparent and you can count the 4 wires. However, does she have a smart phone/eReader/Kindle/music player that she knows works? She could use the cable to test it and see if the device is recognised? Unless Apple are using proprietary connectors of course. I’m an Android man myself.
Actually, does she have a Kindle? That lead is definitely a data lead. Try swapping.