[Sprint  Galaxy Note 4 Q&A, Help & Troubleshooting] The Carthaginian:
I stayed up all night last night working on this, let me update the thread with what I have done so far.

I was looking at some stockish ROMs and I noticed that there were warnings on some of them stating that you needed to have the Sprint OTA 5.0 update installed prior to flashing, which I actually never got. My phone came out of the box with Kit Kat and I never installed the 5.0 update, I went straight to CM12 5.0 instead. So I had a theory that there might possibly have been some sort of network data profile, etc or something out of that official 5.0 OTA that I never got that was somehow causing me problems. I decided to revert back to complete bone stock.

I wiped everything and flashed the N910PVPU1BOB7 file (MD5 = 7304e42cf0e241553d8db9e3c3eeed81) which was the official Sprint 5.0 OTA. Loaded it up, updated the PRL, Network Data Profile, etc, etc, etc.... everything works (relatively speaking...... TouchWiz sux balls of course). I have LTE signal, I can send/receive calls, I can send/receive SMS... all good.

So at this point I decided to re-wipe and flash AICP, with the emotion Kernel (latest builds on all). Load it up.... same problem as before. I have LTE signal (stronger than on the stock Sprint ROM), I can send/receive calls, I can receive SMS but I still CANNOT SEND SMS :confused:

I tried a few things at this point. I tried to manually reset the Sprint network connection on the phone by dialing ##72786#, this did not work, it returned an error "incorrect MIM code". I tried the *#*#4636*#*# that I have seen suggested in multiple places, this also did nothing, it returned an error "incorrect MIM code". I also noticed on the "mobile networks" tab, and this is true for BOTH CM12 and AICP, that it has the setting at "Global" by default and everything works with exception of sending SMS. Now when I click that tab it only has 3 options LTE, 3g, 2g.... for some reason "global" is not an option, neither is CDMA. Whenever I select LTE it automatically drops me from the Sprint network PERMANENTLY until the ROM is re-flashed there is no way to reverse this. I cannot even dial the manual programming codes "*#* etc" as it just simply says "no network service". If I try to automatically connect to the sprint network through the network operators tab it does in fact find Sprint as my provider, however if I click on Sprint to connect it processes for about 2-3 minutes and then simply returns an error of "cannot connect to the network at this time, please try again later". Again the only way to reverse this is to re-wipe and re-flash again which puts it into the unselectable "global" network setting by default where then I will have LTE signal, I can send/receive calls, and can receive SMS but not send SMS.

So that is where I am at, I stayed up all night last night wiping, flashing, and testing different things over and over. Nothing seems to work 100%, except the stock 5.0.1 OTA which is what I am on now. I really hate TouchWiz and for some reason I get a much weaker LTE signal on stock compared to either CM12 or AICP (I have no clue why this is). I am really at a loss here why everything works on the custom ROMs except for sending SMS..... willing to try almost anything to go back to a custom ROM.

Let me know if you guys have any other ideas.