Anytime that a computer goes through a major upgrade it is a good idea to run through a repair of the disk permissions (Apple dropped this feature in OS X El Capitan).  This will likely resolve connection issues with USB devices. 

• With the instrument connected to the USB port  go to your Applications folder and select Utilities > Disk Utility.  This application usually will open with the First Aid tab selected however if it does not click on that tab. 
• Select the Hard Drive and then click on Repair Disk Permissions.  This may take a few minutes to complete depending on the size of the drive.
• Once that is complete reboot the Mac operating system then launch the application.  (While normally rebooting is not necessary we have gotten better results adding this step in.)

You should now be able to connect the device to your software once again and continue to work as normal.

If you continue having issues with getting the device to connect there might be something that has corrupted the X-Rite Device Services (XRD) which allows the hardware and software to communicate. First we want to make sure that the Mac OSX sees the device. With the device plugged in, go to Apple > About this Mac > More Info > System Report. In this window select USB under the hardware contents. Make sure you see i1DisplayPro or i1Display3 showing under the USB Device Tree.

If you are not seeing it then the USB device isn't recognized by the Mac in which case I would try another port or even a powered USB hub.

Next, we want to make sure that the X-Rite Device Services (XRD) are showing up. Open the i1Profiler Software with the device connected to the Mac and go to Applications > Utilities > Activity monitor. Do you see XRDD running? If not try installing the services directly:

http://www.xrite.com/x-rite-device-services-xrd/support/d1493