MX5 no signal suddenly

I use AT&T. I could use 3G (HSPA+) a few days ago, but it didn’t have signal suddenly. Can someone help me?

firmware: I tried and


@dakeyu you checked the APN settings?
How about your provider, are you sure they do not have a service maintenance (has happened to me twice)?

@Rey thanks for your reply. I can use the SIM card at other phones. I checked the APN, I think it was no problem.

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