I bought the device used about two months ago. Activated just fine.
Turns out that I cannot text with anyone who uses AT&T or is carried on Sprint (credo).
I have spoken with tech and it has been escalated with no resolution.
Spent hours at the store itself with no fix.
I tried several apps - verizon's built in. messages. hangouts/message from google. textra.
Turned off and battery out for extended time.
Wiped it clean and reset.
Wiped it clean and reset again.
Turned off, disabled or uninstalled all other texting apps.
Only use Textra now.
Verizon support indicates that there is an issue with the other carriers - the messages are being sent but not received by them. But, that does not explain why I don't receive from them as well.
Does anyone have any suggestions or fixes?
I am not sure what might be causing the texting problems, but I did notice that you mentioned that you have had the phone for about two months and you are running kitkat. The Note 4 is now up to Lollipop 5.0.1 with the latest update around August 10th, 2015. Maybe the texting problem is because you are behind on updates.