How to fix Unreal Engine 4.18.1 stuck at Initializing 45%

I have just installed the new 4.20.1 version on a 2012 macbook pro.

It took 45 mins to initialize for the first time. It froze at 35% for about 35mins… Allowing Ue4 to bypass the firewall got it started again, sat at 45% for another 10mins then the rest was speedy.

The first time just takes a while.