Release the button once the "Device connected in flash mode" message appears.
Before you flash, understand these three unique issues for our LTE model: Firmware Change Update on SONY SGP771 Xperia Z4...
: Once finished, tap Install in the Notification panel and follow the on-screen prompts. Release the button once the "Device connected in
Breathing New Life into the Legend: A Practical Guide to Firmware Updates on the SONY SGP771 Xperia Z4 Tablet Firmware Change Update on SONY SGP771 Xperia Z4...