Cannot download using Mac

Hi,
I have a Mac running Mojave version 10.14.5 ( a recent update ).
Before the update I could download to an Arduino Nano no problems.

Now it will not download, has 10 attempts saying it cannot sync. Arduino software is 1.8.10. Have disabled "Rootless System Integrity" and "Gatekeeper". Also tried multiple Nano's and cables. Any ideas ?

Try the old bootloader option under tools -> processor