Please make sure that you are enabling one of these below payment gateways for your store:
- Shopify Payments
- PayPal Express
For further information, please visit this guideline: https://globosoftware.net/kb/required-setup-payment-gateways-on-shopify-store
In case the problem still persists, please drop us an email at firstname.lastname@example.org so our development team can dick into the issue.