Can't upgrade to 56 beta 2 from beta 1...

I have tried six ways to Sunday, each time the router AC68U times out. Here is what I have tried:

- Normal upgrade page from Merlin firmware
- ASUS recovery - putting router in recovery mode
- I've unplugged USBs and rebooted
- started with WPS and power button
- reset with reset button and power on
- tried to load ASUS firware and merlin 55 and merlin 56 beta 2 - all for the RT-AC68U
- I've tried windows explorer and chrome
- each time it times out, reboots and comes back to the version...

Can't upgrade to 56 beta 2 from beta 1...