Nexus 6P Early Shutdown Problem

My Nexus 6P shuts down early, while still having 80% to 90% battery left and it doesn't start up unless I connect it to the charger.

Ive tried several things, like clearing the cache, doing factory resets but nothing works. I contacted the manufacturer and they refused to fix or replace the phone because it's over one year warranty. Any ideas on what to do?

Aubree