No SIM after upgrade and also no sound when using headphones

So hey guys,
I just recently bought Meizu MX4 PRO and I have come across two really frustrating problems that make me question my purchase.
The first one is that I upgraded from the 4.2.8,2C firmware to the one and while my SIM card was working properly -all signal, 3G and 4G - now the phone doesn’t seem to detect it at all. It just has a NO SIM indication on the home screen.
The other problem, that I had on both firmwares, is that whenever I connect any pair of headphones on the phone I can only hear system sounds, ringtones, and phonecalls. I can’t hear any sound at all that comes out of an app, such as spotify, youtube or even games. Speakers work flawlessly.

Do you guys have any ideas what to do? Any help would be really appreciated. I’m about to lose my mind in here.

Well, after long workhours I solved my problems and I find useful to tell you what I did in case anyone stumbles upon the same situations.
It seems the upgrade wiped off completely the unique IMEI number of my device. Only Chinese devices tend to do that. That’s why there where no SIM card detection at all. To solve this I had to reset the IMEI number (it is written at the back of the battery and on the box) with the precious help of google.
When I did restore the SIM card number I had given up on the sound problem and had come to terms with it. While I was randomly upgrading Google framework (or services, I’m not sure) to fix some play store troubles the sound began to work flawlessly and has continued to do since. It may be circumstantial though, I’m not sure. When I bought the device this google service app wasn’t upgraded to its newest but I had not way to know this since the google apps worked pretty well. Had I known, I wouldn’t have been through so much trouble.
It’s worth mentioning that both MEIZU services and the vendor from which I purchased my phone told me to do some meaningless and completely useless ROM updates to fix my problems which resulted in to nothing sort of a fix.
So there you have it.

Meizu MX4 Pro

How did you reset your IMEI?

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