To check if a subscription can be extended (is not expired) we can use a diagnosis tool: CHECK SUBSCRIPTION
Provided that you entered the correct values (no extra spaces and so) but you get an error message as "Something went wrong with your entries.", it means that your subscription is already expired.
If you placed an order with an expired subscription, the system will put it On Hold for the reason that it can no longer find your account because it was already expired thus cannot be renewed. In order to proceed with your order, subscription must be set from "Renew Existing Subscription" to "New Subscription".