[ZTE Axon 7 Questions & Answers] piet8stevens:
Additional info

OK, not sure I can write down everything as I repeated it so many times until it succeeded. Windows 1.1.1 tool is simple, you find it here: https://xdaforums.com/axon-7/development/tool-axon7toolkit-t3573108

Re. battery, I am not sure that played much of a role. What did help a lot was a windows 10 laptop with device manager open so that I could get some feedback as I was trying out stuff. I also have an Ubuntu desktop but that was not as helpful to me.

From memory, I would say the process that got me out of trouble was like this:

a. Starting point is a device that shows DFU mode in Windows device manager, I believe under a com port. I could get into this state by hitting power button, Volume up and Volume down at the same time.

b. Then, I tried to get to FTM by holding power and volume down for a long time. That did not work. I did work with the phone when it was only 1% charged (but as I said, not sure how much that matters).

c. What was important for me was to realize whether my A7 was on or off. I could find that out because when you switch it off, the windows PC beeps and the A7 disappears from the device manager completely.

d. If I remember correctly, when off, I could get to FTM by holding power and volume down for quite a while (count to 20 or something like that).

e. Once the white rectangle for FTM shows up, I was in business (although it took me many, many tries before I realized this). The signal that I was on the right track was also that the device now showed up in Windows device manager as a Qualcomm HS-USB QDLoader 9008 device under a COM port. That is a hopeful sign. Some Russian web-sites teach you how to get to this FTM mode by opening up the hardware of your phone and shorting some things, but I was not brave enough to do that. 'adb reboot edl' works when the white rectangle is on, but then the A7 disappears again from 'adb devices', so dead end for me (I tried miflash from the windows 1.1.1 tool with the unlock files but going via 'adb reboot edl' never got me to an unlocked phone).

f. With the A7 in FTM, I was able to use the windows 1.1.1 tool to unlock the bootloader again (I got in trouble by locking the bootloader while my system had been destroyed, I think). So, in other words, you switch off the A7, boot it to FTM and then run windows 1.1.1 tool, option 6 to unlock. That gives you access to fastboot. One sign that you are getting to here is that now, during a reboot, a battery symbol with %full shows up on the screen, which it does not do earlier.

g. With fastboot access, you can then flash twrp using the command "fastboot flash recovery recovery_to_flash.img". The recovery to flash is here: https://build.nethunter.com/twrp/zte/twrp-3.0.4-1-ailsa_ii.img

h. Then, I ran into a problem that my partitions seemed to be all wrong - my sdcard was full when I adb pushed a 2.3GBytes zip file to it. Reformatting the sdcard from fastboot fixed that.

i. So, then, I was able to flash the b09 zip (both boot and system) from here: https://xdaforums.com/axon-7/development/rom-guide-updates-to-stock-files-via-t3469484 . Make sure you download the files for the G version. B10 is listed here but does not seem to be for G.

j. Finally, I upgraded to B10 using the zip from the German zte support site here: http://www.ztemobile.de/support/downloads/?product_id=2100. That B10 upgrade however resets your recovery to the standard recovery. So, I reflashed twrp using fastboot.

k. One strange thing I noticed while on B9 and on B10: the phone reports it is a A2017G but the windows device manager reports ZTE A2017U. Not sure where this little disconnect comes from. I did not check this while on B08.

All this worked, sometimes more with luck than wisdom. I am now struggling to upgrade to Nougat from the same ZTE Germany web-site, but I have not figured that one out yet. Note: I have written this down from memory so some details may be in the wrong order. Use common sense at all times.

Hope this helps. Ask more if anything is not clear. I have no clue as to why this worked for me but for some others, they could not find a solution. It took me a good 2 days to figure it all out so maybe perseverance pays off. Good luck.

Piet