How to buy a Plugin again or renew a licence?

I want do buy a Plugin again (Skema 2D Projection), because the activations are full 5/5. I use it on 2 different Pc´s. But on the new one it doesnt work. No Licence it says. How can I buy it again or renew the
Licence! The Developer doesn´t answer.Skema|690x162 Skema2