Thank you for confirming,
Unfortunately, the issues you are experiencing are symptomatic of an internal hardware defect, meaning a faulty power supply or backlight component, though there are many possible failure points. This issue could be a manufacturing defect, but is also often caused by a power event (shock/surge, prolonged over/under voltage condition, etc).
This could also be the result of age related wear and tear; even for a 2015 model tv, that type of failure wouldn’t be uncommon.
There is one step you can take here, both as a possible fix, as well as a diagnostic evaluation:
1) Unplug the power cord from the outlet
2) Wait at least 1 hour (60+ Minutes)
3) Press and hold the power button (on the set, not the remote) for 60 seconds
4) Keep holding power button while plugging back in, and for another 60 seconds after. When plugging back in, go directly to the wall outlet, bypassing any power strips or surge protectors.
If this reset process does not work, it would unfortunately confirm an internal hardware failure.
This is something that would require repairs to correct; if you're thinking about a do it yourself repair, you'll need to be comfortable and skilled with electronics repairs, which could include dismantling the set (removing the back panel of the tv), diagnostics testing with a multimeter, changing out boards as needed, and possibly desoldering/removing and soldering/replacing individual components.
If you’re considering repair at a local shop, you’ll find a typical repair to be around $300 for diagnostics, parts, and labor.
Here are the closest local repair options: http://bit.ly/2x0lDq9
If you would prefer to replace the tv rather than deal with repairs, I can recommend replacement options for you as well.
My apologies for the news,