The easiest possible fix is to try and push the cable into the calculator’s port harder. You’ll have to plug it in harder than you’d expect, you’ll feel a click when it’s properly connected.
If that doesn’t work, this could be the result of a faulty cable. Try using a different ‘mini USB to USB type A’ cable. Trying a different power source (i.e. different computer or use a wall outlet) may work too.
If that doesn’t work try archiving anything important and perform a RAM reset (press the little button on the back of the calculator), there may be something going wrong with the software that’s preventing it from charging.
If that still doesn’t work, you should test if your USB port is faulty. Archive any important information since this will clear your RAM. Get out your mini USB to mini USB cable, a friends TI 84 Plus CE, and connect them together with side A in your calculator. Turn the both on, then on your calculator press [mode] then [alpha] then [s]. Press enter until you reach the Diagnostics screen. Then press  to launch the test. If you’re confused on any of this, there’s a tutorial on how to use the Diagnostics test here. The test you want to try starts at 5:18. Please let me know the results of that test (how many packets succeeded to send and how many errored out).