I'm sorry I didn't see this before you ordered a new battery. This has become a common problem with newer TI-84 Plus CE calculators where they can't charge a flat battery. Since you state the calculator is new, TI Cares has been pretty good about sending a new battery for free. https://education.ti.com/en/customer-support
If you plug the old battery into a friend's older TI-84 Plus CE and charge it overnight, the battery will likely come back to life.