Restarting the phone all the time can be so time consuming. Have you processed the steps to reset the network settings? If not the steps are as follows:
Let me know how it is working after this is completed.
Crud. I know this situation is annoying. I suggest turning off the phone, taking out the SIM, make sure it's clean, put it back in, and restart phone. If you still have the error after that, it may mean the SIM is damaged. You can go to a local store and get a new SIM for free. Hope this helps, let me know.
Sounds good. Here's our store locator if you need it. https://storelocator.sprint.com/locator/
Let me know if you need anything else.
I have a note 5, my 3rd one. It started saying invalid SIM, a LOT! I have to restart it all the time.
I have a note 8, and experienced the very same. After my second sim replacement and they and I provisioning the phone again, that issue went away. Also, if you try to update the prl and profile when their network is down for maintenance, it will show an error too. I have found cleaning off the sim doesnt work. Rest assured, eventually the new replacement sim again will settle in and you will be ok. Anything more than that, would not be network or sim related. I wish you the best. Its note just your note 5, as many others have same issues. Updating during daytime hrs on the prl and profile are best if you do. Have sprint first provision device again when you get a new sim. Then use the code mentioned by another earlier of the keypad to use if periodic call issues or otherwise.