So, I just wanted to give an update and found out that for some reason the credit card statement for that month was not charged the CA tax fee. So I ended up paying the tax and the penalty fee. I don't know why it was not charged and there was no notice that it was not charged.
I was able to pay it off with my credit card thankfully. Though unfortunately, I got the letter about 5 days before the due date due to being in Japan.
Just wanted to thank the community for their help with this. Being in another country and dealing with taxes is always a nightmare for me.
