In the United States, if you process more than $20,000 and have more than 200 transactions, then you are required to submit a 1099-K form to the IRS. This form is generated by Shopify Payments and provided to both you and the IRS on an annual basis.
Did you do at least 200 Transactions in the year + make $20,000 or more? If not, then one would not have been made. If you did, I would contact Shopify Support :)