[XDA Assist] Daftnap:
Hello everyone,

I currently have a Oneplus 3 which is completly unusable and I'm asking for your help to make it working again.

Until yesterday I used OxygenOs 4.0.2 ROM and it was about a moment I was thinking about changing my OS for the LineageOS ROM on Android 7.1.1 .I already did in the past this kind of changement on my nexus 5 for CM 13.0 .

So, I prepared all the files I needed (TWRP, ROM, Gapps etc...) and compared a lot of similar tutorial for being able to do it perfectly and being sure everything will work fine.

Firstly, I unlocked my bootloader though my PC and installed TWRP whithout any problems.

After that, I started the flash of the ROM and the Gapps zip packs. Everything worked and I launched the OS for checking if everything work.

I also wanted to ROOT my phone so I rebooted it and went to recovery again for flashing the ROOT zip from the LineageOS website and I picked the ARM64 one because I saw on internet it was the one needed.

After that, when I reboot the phone onto the system I have to make a "reconfiguration process" on this kind of way : Choose language --> Restore from zero --> Choose network --> Google account.

But, after filed my google account information I was normally able to receive a text for the double checked of my account but never it never came and the configuration is finally unsuccessfull because IMPOSSIBLE to skip the "network" or "google account" step.

I also tried to connect my phone on an other google account without the double checked option and it doesn't work too with this king of alert : " The process doesn't work due to an unknow error. Try again in 24 hours " .

I concluded that the problem come from the ROOT ZIP file, so I put my phone again in recovery and I do a " wipe / factory reset " for doing the exact same process from the begining (installing ROM) until root with this time the ARM ROOT ZIP.

Finally, I got the exact same result with the Google Account problem.

I choosed to do the complete process a third time with this time the SuperSu v2.79 ZIP file .... Result still the same.

Finally, I stoped trying to root my phone and I did again a "Wipe / factory reset" for just installing LineageOS and the Gapps pack. And I was suprised to see that the same problem continue to happen ! I wipe the phone and did again and again and again.

But, after all of that I choosed to do it on an other way. I saw on internet that " format data" through TWRP could be a solution for cleaning everything and start from zero. I did it and the process failed ....

From this point, I am with a phone which can't do anything and which saying that's impossible for it to "mount data" and other but I prefer to show that part on pictures. I think it'll be better for understanding (Excuse me for the pink because my HTC One M7 spare phone) :

Above there are the information that TWRP give me when I start it :

On an other hand, the phone is recognize by the computer just as a multimedia device and it's impossible to write on its memory or just having access on it :

I hope I was the most clear as I could and hoping as well for an existing solution for my issue (in better case with LineageOS on it with root working ! But I don't want to ask to much !).

Also, I am french and I apologize for my english if it can be weak sometimes.

Thank you in advance. I'll allways available if you need further information.

PS: Since my bootloader is unlocked I have these both pages when the phone boot (Picture 1 and 2) which normally permit me to boot onto the system, recovery, fastboot etc .... (Picture 3) but in reality there is NOTHING happening and I always have to do it on the classic way if I want to boot on recovery or fastboot (hold power button + ..... etc...) :