Among the numerous problems that one could face on a Samsung Galaxy device, the "Not registered on network" error is quite common. If it happened to you as well, here is what you should know about it.
Is it something serious?
Every message that pops unexpectedly on your Smartphone's display tends to scare you. What you need to know about this particular error is that it is not something necessarily serious. In fact, it happens to many people, on different devices from the Galaxy series. Such errors have been reported on Samsung Galaxy S3, Samsung Galaxy S4, and even Samsung Galaxy S5.
Usually, two main situations can trigger this message:
One of them relates to the purchase process and the carrier your Smartphone is registered under, through contract;
The other one relates to some software updates.
As suggested, both of them are fixable, but you will have to eliminate them one by one.
Registration problems and how to fix them
The registration issue most likely occurs with first users. If you have bought the device from a specific carrier, through contract, but you are trying to use a SIM from a different carrier, chances are you will get this error. Carriers tend to blacklist the devices they sell, to prevent customers from using SIMs from their competitors without completing the contract.
To check if this is the case, try to insert a SIM that you know belongs to the original carrier. If that one works and other SIMs, from other carriers, do not work, you have found the source of the problem. Unfortunately, you will have to get in touch with the seller and establish the terms that will allow you to use a different SIM with that device.
However, before you do so, keep in mind that some users reported to mysteriously solve this problem by simply inserting that different SIM. When reusing their initial SIM after the switch, the "Not registered on network" message just did not show up anymore. Therefore, you might check this one before getting in touch with the carrier.
Software problems and how to fix them
Another common cause of dealing with this message relates, as already suggested, to update discrepancies. If you root your device with software that is not approved by the phone's manufacturer, you might end up having different versions of firmware and kernel. If those versions are incompatible with your device, the phone might not be recognized inside the network.
Trying to update your device through unofficial ways is dangerous. At the same time, however, software or firmware that is not up to date could also give you problems. Regardless if you are on Vodafone, T-Mobile, Rogers, Airtel or any other carrier, you could get this error even after the official root.
To get rid of the annoying message, you could:
Surf the web for detailed explanations on how to fix the "Not registered on network" error, from specialized websites;
Try a few simple methods, on your own, and hope it will go away;
Take your phone to an authorized service and have it handled in there.
The last one is, obviously, the safest, but not everyone is that patient. If you want to take the problem in your own hands, here is what you could do:
Things you can try on your own
If your smartphone shows up as not registered, you can try to manually select the Network Operator on that device. You will find this option at the Mobile Networks tab, at Settings, under the Wireless and Network options.
If there is not much valuable information stored on your device, you can take the safest path and initiate a factory reset. This one is said to work most of the times. As its name suggests, it involves removing all the data, including everything from your internal storage. Just in case, do a backup first and then perform the factory reset.
If you know you have been doing some changes into the Smartphone's software lately, you should also check whether the device software and the Samsung Account software are updated and, of course, up to date.
Whenever you feel the problem is too big for you to handle, ask for professional help. You do not want to turn a relatively minor "Not registered on network" bug into a headache bigger and harder to solve.