Although this sounds like a hardware failure, you can try a software fix first.
Try to reinstall the OS. I don’t know if it’ll work for you since your keys aren’t functioning but you may as well try it anyways [https://youtu.be/8HlPgS0elRM?t=10m22s|here]. (Fun fact: the [on] key works because it’s hooked up to the calculator differently from all the other keys)
In the likely event that doesn’t work, refer to [[TI-84 Plus Silver Edition Troubleshooting|this guide]] for troubleshooting and hardware fixes.