You didn't say what model of TI-84 you are using. The older TI-84 and TI-84 Plus is NOT rechargeable via the cable. The batteries supplied with the calculator are standard 1.5 volt AAA batteries. You can use rechargeable AAA batteries in the TI-84, but you'll need to take them out and recharge them in a compatible charger when they start to run down.
The newer TI-84 Plus CE is rechargeable via the supplied cable (USB-A to USB mini-B). If this is what you have, then it would help if you told us what error message you are getting from the OS.
