In early versions of Kartris v1.3, some skins had the viewstate disabled on the currency menu. This means the currency dropdown does not change the currency or stay on the selected currency.
The reason is that viewstate is disabled on the currency menu in some skins. For example, in the skin's master page, you will find this:
<user:CurrencyDropdown ID="UC_Currencymenu" runat="server" EnableViewState="False" />
Just need to change this to:
<user:CurrencyDropdown ID="UC_Currencymenu" runat="server" />
After this, the currency selection should work correctly.