This appears to be a major problem with all MAC owners how comes Mcafee haven't got a fix out yet. I disabled all firewalls including Mcafee's own and still no update. A very poor product.
I have had at least one MAC update since my last message when I got back from sick leave and all now appears to be working, I'm still on 10.13.5 but I'm not sure what the updates were. I will need to monitor it for a while.