I used that plugin a lot and was sorry to see it working less and less despite it was very useful. As it seems not updated anymore, as I did I would advice you to switch from using that plugin to creating variable products for your samples. It’s quite easy to set up once you have made some tests, every variation may have its own caracteristics and price, and this will allow you to let that plugin aside.
I searched A LOT for an alternative, made A LOT of tries to update the code of the plugin, making it work as much as possible, and at the end I don’t have any regret for forgetting that idea and switch to variable products.
