I'm Ann, from the team here at Shopify :)
There might be cases where people have been successful in using a virtual credit card in order to pay for their monthly subscription, however, this isn't something we support. That means, that it might work, but at this time, it's not guaranteed.
Additionally, there have been cases where one month the card accepts our charge, and the next month it's declined. You can reach out to the provider to see if they can shed any more light on this, or you can try testing a card like that in our platform, but again, there's no guarantee that it will go through.
Your best bet will be to use a valid physical credit card that accepts both international payments and subscription type purchases.
I hope this helps! If you have any more questions or concerns feel free to reach out to us on this thread :)
Have a great one,