I had the same problem. Finally I found how to fix the issue: International --> Localization --> DISABLE the option "Set default country from browser language"
I am using Prestashop v 8.1.5
The problem appears when a link is opened for the first time (via Google or by directly opening the link). The first time the page is loaded, the price is displayed without tax. After refreshing or opening another page, the price with tax is displayed. This can only be played through the incognito browser.