It can be seen from the screenshot above that the tax rate column is empty and that the sales price of the product TTC is equal to that HT.
It can be seen, however, that each product has a set of associated tax rules, in this case one of the groups defined for France. So why is the tax rate column empty?
Understand that a tax rule group does not give a single, fixed tax rate but rather a tax rate specific to each country, so that VAT can be applied to the buyer's country.
Therefore, a false or non-existent tax rate probably indicates that you are asking the program to calculate the TTC prices in a country other than France, specifically in a country for which the group of tax rules "VAT 20%" associated with the product Gives no tax or tax different from that which would be applied to a buyer based in France.
Indeed the program allows to exit catalogs for any country / state, customer, etc ... therefore for contexts giving different tariffs.
This is set in the drawer "Calculation options", for the country choose "France", this is in principle the default choice, but it must have been modified inadvertently
The following result is obtained:
The tax rate column is well documented and the tax rate defined for each product, for a buyer based in France, has been applied to the sales price, excluding VAT, to calculate the good sales price inclusive of tax.
Next week we will see how to print a complete catalog of your shop.