As SIM cards have shrunk, the points of connection between the SIM and device have become smaller. This means that simply pressing the SIM in "all the way" can sometimes miss the delicate connection between the two. Sometimes, simply pulling back the ...
Power your device off, remove the power cord and battery. Take out the SIM card and put it back again. Some routers have a metal cover that clicks in to hold a SIM down, try adding a small cut out piece of paper to add resistance and help the ...