1. To fix invalid IMEI on Samsung Galaxy S4, the first thing you need to do is to download ODIN V3. 09 zip from the link and then extract it.
2. Then download Samsung Galaxy S4 IEMI null fix zip from the link and extract it on your computer.
3. Now open the ODIN, and then select the PDA option that you will get on the right-hand side. Click the PDAbutton.
4. After clicking the PDA button, a pop-up message will appear on the screen. Choose the .TAR file that you gotafter extracting the Samsung Galaxy S4 IEMI null fix zip file.
5. Go to download mode on your phone. (Press and hold Volume Down, Home and Power buttons at the sametime)
6. Connect your phone to your PC using USB cable.
7. Now click on the Start button on ODIN and firmware flashing will start. (Do not check re-partition)
8. It will take few minutes to complete the installation. Wait for ODIN to complete the installation and thendisconnect the phone from the computer.
You need to follow only these simple steps to fix invalid IMEI on Samsung Galaxy S4.
if this will not work or you already install a firmware file then just download this file flash it in odin in phone n done without any prob