Price was converted twice on checkout page

A price that arrives at checkout converted twice means something other than FOX is converting it as well. FOX applies the rate once, so a doubled conversion is always a second party in the chain.

The usual candidates, in the order worth checking:

• A theme with its own currency or pricing integration. Themes that advertise multi currency support often ship a FOX integration you did not know was there.
• A discount, dynamic pricing or fee plugin that reads an already-converted total and converts it again.
• Custom code in functions.php calling woocs_convert_price on a value that was already converted.

To isolate it, switch to a default theme with only WooCommerce and FOX active and place a test order. If the amount is correct there, re-enable one plugin at a time.

When the culprit is a third-party plugin comparing money it already converted, the fix is usually woocs_back_convert_price — it takes the amount back to the base currency so the other plugin does its arithmetic on the number it expects.