S4 "not registered on network"

[Ali Hassan19]

I was recently overseas and had to use my phone there and got it unlocked via a friend. Apparently, they flashed the device and now it will not recognize my original sim from the carrier I got the phone from. It keeps saying not registered on network and I tried manually searching for network and it says "unable to connect to Koodo (my carrier)". I tried to do a software update but it searches for updates and then does nothing no matter how many times I try to click the software update button.

Any help will be much appreciated!

 

[B. Diddy]

Welcome to Android Central! When you were manually searching for a network, were you using the Settings>Connections>More Networks>Mobile Networks>Network Operators menu? ​Samsung Galaxy S4 - Select network

 

[Ali Hassan19]

Thanks Diddy.
Yes. I took the phone to the carrier outlet. They tried doing the process as you mentioned. It finds the mobile network but says unable to connect to it.
Currently, my network coverage says unregistered sim. However, the sim is working on another phone, so I can only assume that some setting changed while the phone was being unlocked or something.

 

[B. Diddy]

Can you ask the carrier to try a replacement SIM?