This problem occurred without any warning or further instructions, so I am posting this just in case this happens to anyone else.
For a while I have been operating QRP with an Elecraft KX3 interfaced to a MacBook Pro (Retina, 15-inch, Late 2013) via a USB Signalink. The MacBook Pro is running macOS High Sierra v. 10.13.6.
Today, Safari v. 12.0.1 became available among the Mac updates. It was uploaded and readily installed and the computer restarted as required to complete the installation.
Everything looked normal. However, WSJT-X (v1.91 r8747) failed to handshake with the KX3. PTT was no longer possible via Hamlib and the frequency in the VFO ceased to be reflected on the window of the program. The same was true for Fldigi 4.0.18. The problem seemed to be that the FTDI driver for the KXUSB cable was no longer functional or detected by any of these programs.
A visit to the FTDI site for these drivers (http://www.ftdichip.com/Drivers/VCP.htm) allowed the download and installation of the 64-bit 2.4.2 FTDI driver released 2017-05-12 and “signed by Apple” for Mac OSX 10.9 or above. (It is possible that until now I may have been using a 32-bit version of the FTI driver).
Upon installing this driver and restarting the computer the “serial port” or “device” dev/tty.usbserial-AD01W0AF was again readily recognized by the digital software (WSJT-X v1.91 r8747 as well as Fldigi 4.0.18).
73 Jose CX7RT/VA3PCJ