Method 1: Check the Network Settings
For solving this ‘Connection Problem or Invalid MMI Code’ Problem this is the 1st method to fix this Problem. For that, you should check your Network Settings.
Go to Settings option on your device.
Now select Network Connection option.
Follow Mobile Networks
Search Network Operators (It will search for Network Operators)
Select your Network from the list.
Method 2: Activate the Radio to Turn on SMS over IMS
To Fix the ‘Connection Problem or Invalid MMI Code’ Problem, this method is very simple. Just by entering into device information mode and then Activate Radio to Turn on SMS over IMS. You can fix this error.
Go to Dial Pad
Dial *#*#4636#*#* (No need to press the call button, it will automatically appear the service mode)
Select ‘Device Information or Phone Information’.
Select ‘Run Ping Test’.
Click on ‘Turn Radio Off’ Button
Then, click on ‘Turn on SMS over IMS’
Reboot your phone & Check
That’s it, Done.
-The help of Google is taken.
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