Mobile Data 3G/4G stops working after 15 seconds

My mobile data doesn't work. I get 4G/H+ for the first 15 seconds i turn the phone on, and then it stops working. I have signal and can make calls fine, just no data.

This problem began after i went on a trip to South America and put a Sim card over there in my phone. Then when i got back to the US I got this problem. I've checked APN, deleted it and created a new one, and still same problem. I've tried another Sim card and it also had the same problem.

Any advice?

@Rey I was running 5.1 flyme global, now I'm running 6.7 beta Chinese. same problem on both, except with the new beta my GPS doesn't work either.

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