Hi,
same problem for me With E310 Set i received 5 ESC's with v1.2 and one with V1.0 which gave me an alarm.
Update for 1.2 was shown and I said okay thats the Problem. I started the upgrade and nothing finished even after 45 min.
Now i have V255.255 on the ESC
OK, Done! Problem solved by using the Windows Version!!! The Mac-Software is definitely buggy!!
Last night I used the MAC ESC program to do firmware upgrades on the E310... It put ESC in a non-functional state. Recovery was to install the firmware using a PC. DO NOT use the MAC software until DJI updates it!