If your FP3 connected to these computers before, you might want to check two other components: Cable and USB port. I would recommend to try other cables (this one’s data wire might be broken), and you might want to clean the USB port on the FP3 from dust, tiny hairs etc.
If you know another FP3 user, you might be able to install her or his USB port in your device and try if that makes a difference, too. There are also Fairphone Angels in Berlin.