I am running 10.14.5 on my MBP with the latest 5.0 client and it's ok.
What environment(s) are you connecting to? Corporate, lab etc?
There was a thread some time back similar and their upgrade wiped out their host file.
Connecting to a corporate site, I tried working with them and they looked at it but ultimately told me is was my issue since it is on a personal device. My other macbook is 10.14.3 and works fine, it is just this one running 10.14.5 that is not working. I saw the thread about host file but do not know enough about what to look for to see if that is the issue. I have compared the host file on both macbooks and they are similar. The non-working one has a lot of extra stuff in the host file but again, not sure what should and should not be there.
I'd say start by checking in the host file that the name/IP for the corporate site matches.
Are you out of the office or on the corporate network?
I have modified the HOST file to match that of the working macbook with no success. Not sure I edited the correct one though. I connect both at home and at work and neither are working.