Thanks for taking the time to respond 
Yes! it was the cable for me. IAnd after finding one that worked, and connecting successfully, the output of the tail command looked like this:
pi@octopi:~ $ dmesg | tail -n 20
[ 15.038242] Bluetooth: HCI socket layer initialized
[ 15.038257] Bluetooth: L2CAP socket layer initialized
[ 15.038300] Bluetooth: SCO socket layer initialized
[ 15.053041] Bluetooth: HCI UART driver ver 2.3
[ 15.053057] Bluetooth: HCI UART protocol H4 registered
[ 15.053140] Bluetooth: HCI UART protocol Three-wire (H5) registered
[ 15.053365] Bluetooth: HCI UART protocol Broadcom registered
[ 15.228896] Bluetooth: BNEP (Ethernet Emulation) ver 1.3
[ 15.228903] Bluetooth: BNEP filters: protocol multicast
[ 15.228913] Bluetooth: BNEP socket layer initialized
[ 558.511436] usb 1-1.2: new full-speed USB device number 3 using xhci_hcd
[ 558.647514] usb 1-1.2: New USB device found, idVendor=1a86, idProduct=7523, bcdDevice= 2.64
[ 558.647530] usb 1-1.2: New USB device strings: Mfr=0, Product=2, SerialNumber=0
[ 558.647544] usb 1-1.2: Product: USB Serial
[ 558.742754] usbcore: registered new interface driver usbserial_generic
[ 558.742817] usbserial: USB Serial support registered for generic
[ 558.745519] usbcore: registered new interface driver ch341
[ 558.745602] usbserial: USB Serial support registered for ch341-uart
[ 558.745684] ch341 1-1.2:1.0: ch341-uart converter detected
[ 558.748887] usb 1-1.2: ch341-uart converter now attached to ttyUSB0
What cable did you use? I am wondering if that is my problem right now.
Please do not reactive old threads.
To your question:
USB cables come in loading cables with only power wires and proper data cables and can not distinguished.
Data cables usually are thicker and the better ones have ferrites at the ends.
You may have to test some.
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Agree. I just tried a different, better one. And it worked. So test some
Have you verified that the RPI port works by connecting some other USB device to it?
Seems like a different cable solved the problem 