I've been having this problem for a long time, can't remember how much exactly. No matter what I've tried, I haven't managed to get my computer recognize my opo (Cyanogen 13.0).
When I connect it absolutely nothing happens. The device manager doesn't flash (doesn't recognize a new device connected), so I cannot find/update/remove the drivers anyhow.
Developer options on my phone have a bunch of things but none seems relevant, apart from open/close Android debugging (adb) and select USB Configuration (Charging/MTP/PTP etc). I've tried several options, nothing seems to change.
I've also installed some Windows MTP drivers (see here) which were supposedly solving the issue caused by a Windows 10 update, but no luck (which could have been the issue, but can't be sure-I can't remember the last time I was able to browse my phone's memory).
Any ideas? It seems so strange to me that I am the only one with that issue. I know CM was abandoned and was thinking to change to another version, but I can't even move my files right now :(