Hi, I have seen some similar posts, but none that solved my problem.
I have a MKR 1010 WiFi and a Nano 33 IoT and they both stopped showing up in the port list at the same time. My current setup is Windows 10 Home on a Dell G15 5515 with version 1.8.16 of Arduino IDE, but they first stopped working on an older Windows 7 laptop (not sure of the model or which version of IDE).
The MKR CHRG button flashes when first plugged in, but stops after a couple of seconds. The Nano doesn't seem to do anything notable, but just doesn't show up. The port list is greyed out.
I have tried putting them in bootloader mode. I've tried a different cable. I've tried different USB ports and even different computers. I've tried looking in the device manager and they don't show up there either.
My Uno's and Mega's still work fine.
The last sketches still run on both, whether powered by battery or by USB.
Any ideas?