Help please- Yoga 720 15 80X7 shuts down immediately.

Hallo, my name is yuval. first of all, sorry if I putted it in the wrong category, I’m new her.
So here is my problem, about 5-month ago I bought a new lap top of “Lenovo yoga 720 15” 80x7” from “best buy USA” and took it back to my country outside of the continent.
When I first started to use it, it has an immediate major problem- “no charging just plugged” so whenever I unplugged it, it would show me that I have no battery and shuts down without any notice.
After struggling with the problem and trying to fixed it by myself, I gave up and sent it to Lenovo USA (I am not from the states so it costed me a 100 $ for the shipment).
They fixed it and replace the battery
About a month ago I got the laptop back from Lenovo – fixed and everything worked fine until a week ago when the laptop began to spontaneously shuts when unplugged but this time only when decreasing to 20-50 % battery.
The charging works and when the laptop is plugged it won’t shut down at all.
I tested the hardware with some of Lenovo’s software and everything looks fine I tried to use a temperature app and everything looks fine as well.
I don’t know if it is software related or HW, really hope it is the first one, I saw that maybe it related to “ME region” which I don’t know what it is.
I will be… so! Much grateful if some can help me with this problem. I’m a fast learner and can follow instructions easily

Sorry Im really desperate and run out money for another shipment to the Lenovo USA.