Question PLEASE HELP - Stuck in Loading

Hi guys,

I need help. My kid's Asus TF300T suddenly got stuck at the loading process. I turn it on, and it keeps loading and then reboot itself and kept loading again. This keeps going forever.

The bootloader is unlocked and I had a custom ROM on it, though I don't remember what it is.

I am still able to enter recovery (TWRP 2.4.4.0) while pressing the vol - and Power buttons.

But what else can I do? How do I get the tablet to work again?

Thanks so much.