Cannot do the factory reset of Sony Xperia Z3 with +/- volume and switch on/off buttons

[kiselev.vadim]

Good afternoon. I have forgotten my password on my old Sony Xperia Z3. There is no way to reenter with my Google account for this model. Sony support haven't had a possibility to help me, neither do Google support. Now I am desperately trying to do factory reset with volume and switch on/off buttons following numerous instructions on the Internet. But no combination of buttons can allow me to enter the reboot mode and choose the necessary option. Please advise me with this problem. I am willing to erase my old data, as I copied it before, and I would like to continue using my phone.

[EYuliyanov]

That's strange.. it should not have to happen..

Also it's not a problem for me that the interface is un Russian, I'm from Bulgaria 😉.
I'm trying it with my Xperia T3 and get the same error..
Let me some more minutes to find if Sony has deleted the support for Xperia Z5 or under or the Sony server is not online now.

[EYuliyanov]

Ok, so server is online i just tried it with my Xperia XZ1 and works.
It might be something with oldest devices...
I checked the Xperia Companion unsupported device list and Z3 is not there, so i can't be 100% sure what is happening.

Also, mention that when you are installing drivers, Xperia Companion should be closed (right click & close on Xperia Companion icon on the taskbar) and none device connected.
If the device turn on, charge it to 100%, on oldest devices the battery may be lost capacity and cause errors when connected to computer.
When the device is correctly connected the notification led is green.
Keep trying it.

[kiselev.vadim]

Finally! Your link to the programme:

https://pastebin.com/WFSEsTgR

helped me to reset my phone to its factory settings. So, I have done this with Sony Mobile Flasher.

Thank you so much for devoting your time and help which has led me to the positive outcome=) 

[EYuliyanov · Accepted solution]

Glad to help you.

Despite is an unofficial method that I found, is great that functioned and helped you.