We have two DSO X3034A scopes, and both have experienced the same problem of flickering keypad and no display after turned on.
Following someone's suggestion in this form, we rebooted each scope 5 times and got it to work (kinda). Now, we have to keep on reboot the scope a few time in order to get it to operate. It was suggested in this site that we should upgrade the firmware inside the machine so it may resolve the issue. We tried to install the new firmware downloaded from Keysight's website (ver. 2.41). However, it keeps on showing error during installation.