You must be absolutely sure that your USB cable supports the data connections. Many cheap cables do not, and can be used for charging only.
Thus I mark all my USB cables which support data with "data" on them.
Your other options is to go and buy a USB cable that is made specifically for data and make sure that works before looking for other problems. Don't forget to mark this one with "data" or just a "D".
In addition, try these things:
- Look at a specific cable to see if it supports data. Does your cable connect any other device/phone/ereader to your laptop? If so, the problem is your Kobo, not your cable.
- Does your cable connect any other device to a different pc? If so the problem might be the laptop USB ports.
- Did you try another USB port on the laptop? The laptop port might be broken, or the data lines might have disconnected. As far as errors go, dry solder joints are not uncommon.