Can I ask what payment method you are now using? Are you using a credit card, debit card or PayPal as a payment method? Also, if you care using PayPal, could you make sure there are enough funds in your account to cover the cost of the outstanding fees? If you weren't sure what the total outstanding fees are, your invoice would have been emailed to you! The email account you would have used as your account owner email is the best one to check, as any correspondence from Shopify will go to that account.
Could you check your account to make sure the funds are there and let me know how you get on? We can take things from there!
Social Care | help.shopify.com