Tax not calculating on 2.0.452.100125 VM4.4.6 11109 J!5.2.4

[frederi80]

We are setting up a test site using latest version of Joomla 5.2.4, Virtuemart 4.4.6 11109 and RuposTel One Page Checkout (2.0.452.100125).
When opc is disabled virtuemart calculates tax properly, and updates order.
When opc is enabled, tax is not calculated. I also noticed that for some reason, if I hit refresh/reload on the browser, the customer information is erased?
This never happened on our older site when we used RuposTel One Page Checkout 2.0.348.210917, virtuemart 3, J!3.
Usually if we reloaded the browser, the customer data would remain.
Can you help us troubleshoot? We copied all of our settings from our previous setup, but we are having issues on the newest version.
Thank you.

PS if it helps, I'm trying this with template Virtueplanet - Smart