Solution 1: Remove Battery and SIM Card
Power off your Android phone and remove both battery and SIM card.
Wait for 5 minutes and then insert the battery and the SIM.
Now power on your phone and check it. If still receive the Mobile Network Not Available Error, then follow solution 2.
Go to settings and open Wireless and Network settings.
Now tap the Mobile Networks.
Tap Network operators and Select automatically. That’s it.
Also check your software is up to date or not. If not, then update it.
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