How to fix “Connection problem or invalid MMI code” from xejel58677's blog

I’m sure most Android users have at some point received a message saying “Connection problem or invalid MMI code”. This can sometimes be so frustrating and so painful to deal with. The “invalid MMI code” error prevents calls and texts until resolved, disrupting communication.

There are several problems for which the error message “Connection problem” or “Invalid MMI code” appears. Service provider or SIM card problems are likely the primary cause of this issue on your smartphone.

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