Sending payment links to your customers is currently unavailable in QuickBooks Online - International. Merchant Services only accepts payments from banks in the United States.
For the time being, I recommend looking for a third-party app that can integrate with QBO and allow your customers to pay online.
To know more about how invoices and payments work in QuickBooks Online - International, here's an article for your reference Invoices and payments.
Please let me know if there's anything else I can do for you or if you have any further questions about invoices and their payment links. I'd be delighted to lend you a helping hand. Have a wonderful rest of your day!