Hello,
Just wanted to say a quick thank you for being our valued customer. We take all customer inquiries, requests, and comments seriously and do our best to help in whatever way possible.
First of all, duplicating serial numbers is not a free feature. If you want to duplicate serial keys, you will be needing WooCommerce Serial Numbers Pro in the first place.
Also, you cannot use the same generated or imported serial number unless you enable the option called Duplicate keys. In addition, a customer who has already got a serial number will not be able to get the same serial number is not a feature.
The feature is needed only for returning customers. The customer must log in to the profile he used for his first purchase. In case the returning customer signs up for a new account and purchases another serial key, it will not be possible to recognize whether the customer is returning or a new one. In addition, many sites allow guest user purchases. This is why the option is not included.
Still, we will share your query with our development team and will try our best to straighten things out.
We value your business and look forward to serving you. Please write to us anytime if you need help with another request in the future.
Thanks
PluginEver Support Team