The following conditions must be met for a 0% VAT purchase to be possible.

I. When entering your company details, you need to enter VAT-EU number, which will be verified.

The number is verified automatically when saving the data.
The process of checking the number may cause the page to be suspended temporarily.
If the number does not comply with the VAT VIES, the following message will appear

"VAT number not found"

You can check your number here:
https://ec.europa.eu/taxation_customs/vies/?locale=en

II. The shipping address must be identical to the address on the sales invoice.