Signed up just for you since I might have a solution which at worked for me.
I uninstalled current 1.14.0.xx-version and installed 1.13.9.x instead which I found by switching version numbers in the download link on the main download page:
I updated PMS to 1.14.0.5470-9d51fdfaa-OSX earlier today on OS X 10.14.2. Previous version worked fine, but I received notice in Plex Server GUI that a new version existed which I chose to install/update to. After that PMS stopped running.
When I open the application PMS starts to load and I get the little PMS “Icon” in the top right corner, but soon after it disappears/Plex quits. As I don’t know how to run the application in terminal or get log files etcetera I don’t know if the error code(s) are the same, however re-installing the application according to the guide for uninstalling did not help.