[G4 Q&A, Help & Troubleshooting] ayoub90:
Ok I will start from the beginning

First I tried to upgrade my phone to Marshmallow, so I went to this link http://storagecow.eu/index.php?dir=Xda/LG+G4/ then opened H815 then went to inside Marshmallow folder and downloaded the Europe version (I don't remember if it was the C or D, but I think I picked the H81520C version )

When I started to flash using LG Flash Tool 2014 the process stopped and it gave me error message (in the flash tool not in the device), and nothing happened to the device of course because this error appeared after checking process for the Kdz file, so every thing was ok.

But I told my self may I can flash the lollipop Firmware for Europe version too, then I'll try to get the OTA update from Marshmallow...and here when every thing started. After successful installing for the Lollipop Europe version (I picked this time the Europe general H815B from the same link) I got the NT Code error message on my device and my device signal is gone, like I don't have operators in my country. I started to research about this error and I noticed then that many people got similar one but with two differences.

The normal error message has values inside it for MCC, MNC and supset the message says "Current Version is not available for user. Can't find matched cust for NT-code mcc/mnc [xxxxx] subset [xx]" and instead of (X) you will find numbers or "F". In my case I got the same message but with empty brackets.

The second deference here is about the network signal, most of people who got the message (with values not empty like me) still have their signal work.. unlike me.

some people could solve the message by editing the "cust_path_mapping" file using the values in the error message as I explained before, but I didn't got any values so I told my self "the new version cause that error and that may be because the different bands"

I tried to search for the default version for my device which was H81510p as I remembered it , but sadly I couldn't find and Firmware versions end with 10P (just to be clear...it's not H815P...but I meant my version was H815T V10P)

I was confused so I choose to try another firmware. I piked this time H815P...that's because H815P used on UAE which considered in the same area here in Egypt and we both use some similar bands, but the problem still there.

In that moment I tried to go back for H815T Firmware with any versions from China (Honk Kong) and Australia, I tried the V10c , V10b and V10h ...and still no improvements.

My last tries was about changing the NT Code inside the hidden menu as I explained too..and I want mention that at the first..when I got the NT Code message with empty brackets..the Address inside NT Code in the hidden menu was like : "0","FFF,FFF,FFFFFFFF,FFFFFFFF,FF"

but when I changed it trying to put my country code like this : "1","FFF,FFF,FFFFFFFF,FFFFFFFF,20" I got the NT Code error message with same values I entered in that long address...so the message changed to "Can't find matched cust for NT-code mcc/mnc [FFFFF] subset [20]"

And here when I noticed the relation between this long address and the NT Code error message besides the cust_path_mapping file

The strange thing is...I couldn't change the address to it's first values..I mean...if I put 0 instead of 1 ...I got "NTCode write error" and nothing changed...but I can easily change the last two digits with any thing and I can go back for example to FF if I want. just the first number won't be changed to 0 again

I think that's all...do you have any conclusions ??

Here is screen shots from my Version info screen....the NT Code is now just "0", because I tried to delete it

http://imgur.com/a/yZDkp