Hank here from Shopify.
Were you always set up with PayPal when you had your trial active? Or is it only since the payment declined that you are trying to pay with PayPal?
As you mentioned, if based within the United States, you are unable to use PayPal as a one-time or recurring billing method, but outside of that, you should be able to in countries where PayPal operates.
What error message are you seeing, is it just the invoice failed message or multiple? Or are you seeing anything when you log into your PayPal account? It should show any error messages within your account, and you will be able to resolve the issue presented.
Let me know how you get on, or if you have any additional questions.
All the best,
Thank you for the additional context.
I can confirm that message is an error with your payment method you are using. As you mentioned you are using PayPal, I would recommend logging in to your PayPal account to see if there are any error messages showing which may shed more light on the possible issue.
Then if still not seeing anything, you can reach out to PayPal directly, to query why the payment is not going through, once you ensure enough funds are there to cover the invoice.