Go back through your Shopify store > settings > users and permissions > select account > and update the pin from the default. I just went through the same thing. Hope this helps!
Hi All: this was helpful for me to find where in Shopify I create my PIN. I did create it but when I type the PIN in the Shopify POS app on my phone, it does not work. It seems like Shopify sees me as a staff member (probably needing additional authorization) but I am the store owner. Any suggestions will be greatly appreciated. Many thanks!