Boot issues... (ticket 18011468)

If you have a spare drive then I would suggest you roll back to 4.2.19. Down load 4.2.19 and have it readily available on your PC. Then install the spare drive and see if you can get the unit to boot with the spare drive. (ReadyNAS units need at least one drive to boot.) If it boots, once it has booted, open Frontview and go to System and then click on update. Do not check for update. Instead, click on the local tab and then browse to the location of the saved 4.2.19 file and initiate the installation. Once you have reinstalled 4.2.19, shut the unit down and remove the spare drive. Then install the disk set, being careful to put each drive in it's original bay (marking the drives, at least temporarily is a good idea). Then on boot, go into the boot menu:

Ultra 6 / Ultra 6 Plus / Pro 6

To access the boot menu:

Power off your unit.
Using a straightened paper clip, press and hold the Reset button.
Press the Power button to power on the unit.
Continue to press the Reset button until the status display screen shows an boot menu message.
Press the Backup button to scroll through the boot mode options.
Press and release Reset button to confirm your boot menu selection.

The system boots in the selected boot mode.

The first option will be the normal boot, the second option will be the factory default (caution this one will wipe your drives) the third option is O/S reinstall. This is the one you want, as 4.2.20 T32 is on the drives and 4.2.19 is now in flash memory. It will use the OS in flash memory to overwrite the OS on the drives. When finished, hopefully it will boot normally. If it does not, your remaining option is to contact technical support via an online ticket.