[T-Mobile Samsung Galaxy S 5] Nateg900t:
Nf6 to nk2 saga

I went through a similar frustrating experience with missing Volte and wifi calling stuck on enabling with my Samsung Galaxy S5 G900t on t-mobile.

I was running NF6 for over a year, having done the Mobile Odin +inject root update to NF6 (with pc Odin bootloader/modem update to nf6) from an earlier build, while keeping my knox 0x0. (I'm not sure why, given the phone is now well out of warranty.)

Perhaps always or sometime over the last year I completely lost the Volte option in the call settings menu and the wifi calling switch would just get stuck on "enabling" when turned to the on position and the only way to turn it off was with the quick notifications toggle. There were no error messages like the reg99...

Given I planned some upcoming international travel where the wifi calling may come in handy, I really wanted to get it working.

First I was searching to see if it could have been my Xposed, with the rootcloak, xprivacy, and minminguard modules. I found a few posts of people with the same enabling problem and xposed/xprivacy but nothing to narrow down the problem/fix.

Strangely, when using Samsung Phone info, of the 4 lines that listed my version, the CSC was blank. Looking in /system/ there was no csc folder.

I didn't want to lose my setup/apps/data, and because I was knox 0x0 without a custom recovery, I couldn't really make/restore nandroid backups. (perhaps I could make them with adb? And I'd used obackup and online android backup in the past, but never had to figure out how to restore if the time came.)

So,I downloaded the stock nk2 tar from the stock firmware thread and applied that, not wiping user data and injecting root, but not injecting mobile Odin with mobile odon. The reboot came up ok, and I still had root, and my data, though I think S health was doing the force close thing. Then I used pc Odin to install the bootloader/modem separate downloads and they seemed to stick. But my CSC line was still blank. I did the bootloader/modem files again after pulling the battery, and turned off auto reboot, and then after flashing I booted into recovery and could see the text about a multi-csc having been successfully applied. But csc still was missing.

Then I decided to flash the whole nk2 tar (with the cp, second one from top section?) with pc Odin, not wiping data, but clearing Dalvik cache.

This at least gave me nk2 on all lines including csc in samsung phone info, and the volte option was showing up in the settings menu, but no progress on wifi calling, still stuck enabling.

So I used titanium backup to backup all of my user apps and data (and sadly not my sms history) and booted to stock recovery and cleared data and cache, and booted up to the setup screen.

This gave me the chance to setup a new dropbox account with 50gb data for the year, and after logging into a few accounts, I noticed wifi calling was working!

But samsung backup and restore was trying to restore my sms/mms log from the cloud and kept erroring out and I quickly noticed that my messaging app was freezing when trying to do nearly anything in it. So I had to wipe data again, and this time only restore call rejection settings.

Then i followed the directions in the nh5/nk2 root with ne6/towelroot thread, installing the ne6 bootloader with Odin, disabling lookout, running towelroot and supersu, disabling knox, then booting back to download mode and reinstalling the nk2 bootloader.

Success! Volte and wifi calling still there and working and I had root on nk2 now.

I restored my apps (1 by 1) with titanium backup and rebooted a few times, making sure wifi calling was still on, tested a few wifi calls.

Then I installed xposed again with the installer and after a reboot my modules were already active, and wifi calling still worked.

Finally, I had to go through each section of settings to make sure that i selected all of the previous options thatI manually copied down into a text file in case I ever need to do something like this again.

Hope my experience/story helps anyone else who finds themselves in a similar situation.

I think the moral of the story is that I should stop buying phones that go out of their way to restrict the use/ability to block ads and apps from accessing the Internet when they don't need it. And i am thankful for my microSD which allows me to easily keep titanium app backups (and nandroid when finally give up knox 0x0) that survive a full reset/data wipe, to get me back in business within a few hours instead of days reinstalling and logging into and configuring apps.