u/Tricky-Type8034

I live in Vietnam, I use Viettel as my ISP. Like the title said, my internet dies every day at around 11:30pm for no reason and doesn't come back for a few hours. My router blinks red on the small light on the front of the router when it can't connect to the internet. It does come back the next day, but only if you force it to turn on by pressing the long button on the front of the router. Is it my router's fault, or is it my ISP's fault?