As of today, the power cord light is always orange, and the battery is always at 99% charged. The cord has been plugged in all day, as it always is. The light was always green before today, and the battery was almost always 100% charged. What does it indicate and how can I fix it? Thanks.
That battery could be getting a little old. You may want to check its condition, as it could be nearing the end of its life.
One other thing to try is to reset the SMC, which gets all the micro-controllers back in Sync:
How to reset the SMC of your Mac - Apple Support
What Model-year MacBook Pro 13-in?
Retina 13 inch early 2015