I have a Galaxy Note 4 with Sprint. Maybe once a week, I get a notification telling me that there is no Sim card. The Sim card has never been removed. This started after I had the phone for 3 years with no problem. Also, this notification comes with a phone lock out from Mcafee where I have to enter my pin to unlock it. I contacted Mcafee about this and after an hour, they had no solution. All they did was give me a set of scenarios which would cause this, all of which did not apply to my phone. They tried to attribute it to Internet congestion. If this were true, this would be happening to many people all of the time, including my wife who has the same phone, purchased at the same time as mine. I am stumped. Please, can anyone help?