Thanks for all the suggestions.
- I am using Windows 10 and yes, it is updating constantly.
- I have tried with 2 laptops, same problem.
- I have checked that the USB menu of my phone (in the Developer Options) is set to MTP and that USB Debugging is set to On.
- I have tried to access the phone with Smart Switch for Windows 10, the phone is not recognized either.
- I have a grand total of 6 of these cables and none of them let me access the phone (but they all charge). At this point, I'm thinking that the cable I was using was a data cable and is now broken, and that the other 5 which I have never used with this phone, are charging-cables-only. We'll be buying a new charging+data cable tonight see if this solves the problem unless someone here has another idea for me to try.