Hello,
we tried to reproduce the problem in our environments, but without success.
Everything works fine with the free version. The problem may be related to the specific version of the free one you are using.
As we continuously update or software, I recommend you to install the latest version of it : https://it.www.ads-software.com/plugins/woo-price-calculator/.
Here is a link from our documentation on how to do that : https://altoswebsolutions.com/manual/woo-price-calculator/update.
If the problem persist, it mean that is a problem of compatibility or another plug-in is causing the issue.
To find so, you can create a plain test environment where you install just WordPress, Woocommerce and WooPriceCalculator and test it.
Waiting for your feedback.
Best regards.
Naidi
AT798