Diagnosis
This is almost always a backlight failure. The screen's LEDs have likely gone out, but the main board and sound system are still running. It's a common point of failure in many LED TVs, including this model.
How to Fix It
This isn't a user-serviceable fix. Your options are: 1) Contact Insignia/Amazon support if you're still under warranty. 2) If out of warranty, a local TV repair shop can replace the LED strips, but the labor cost often approaches the value of the TV.
If That Didn't Work
If the sound also cuts out, or the TV seems to restart, it could be a main board power issue. Try a full power cycle: unplug the TV from the wall for 5 minutes, then plug it back in and try again.
Heads Up
Shining a flashlight at an angle on the black screen might reveal a very faint image, which confirms the backlights are dead. If you see a perfect image with the flashlight, it's definitely the backlights.