stuck on loading screen upon plugged in

I have a TI-Nspire CX CAS that I recently tried to charge. It's been a few months since I last turned it on, and the battery was dead. When I plugged it in, it started loading but got stuck on the loading screen about a quarter way through. I have tried the following:

• Updating the OS via the TI-Nspire Computer Link
• Leaving it on charge for 36+ hours
• Leaving the battery out for 12+ hours

All of these attempts have failed, and I don't know what to do next.