Why does it happen
This warning message is generated by the Currency Switcher auto-update mechanism. During the auto-update phase, the Currency Switcher processes past orders to determine their value in base currency, for reporting purposes.
What does the message mean
The message indicates that you have a past order which was placed in currency "X", but you don't have such currency amongst the enabled ones. For example, the message might say "Exchange rate for Order Currency "USD" (Order ID: 123) could not be retrieved." This means that US Dollars is not one of the enabled currencies.
How to fix the issue
- Go to WordPress Admin > WooCommerce > Currency Switcher Options.
- Add the currency (or currencies) displayed in the message to the Enabled Currencies field. Note: if you don't want your store to accept such currency/currencies, you can remove it later.
- Save the settings. At page reload, the Currency Switcher will process the past orders correctly.
- Optional. If you don't want to accept some of the currencies you added in step 2, simply remove them from the enabled currencies and save the settings again.
In some edge cases, the message you receive may indicate that the exchange rate for base currency could not be retrieved. In such case, simply saving the Currency Switcher settings will fix the issue. Base currency is always enabled and it's processed automatically, it doesn't have to be added manually to the enabled currencies.