Apple Watch 7

Hi,

I just purchased an Apple Watch 7 on my Verizon account. I got it in the mail today and I could not get it to turn on despite charging it. I went to the store and got it exchanged and this one is also just showing me the charging screen green/red. How long should I leave it on the charger before I take it back and ask for a new one. I don’t understand how I could be so unlucky to get to non working units together. There has to be something I’m not doing right, maybe not enough time on the charger?