Scenario:
- Go to Admin > Settings > Currency
- Click on the "Exchange Rate Settings" tab
- If you have more than one currency module you will see the one(s) you use selected/ticked
- Go to the "Currency Options" tab
- Assuming you have a couple of currencies set (not just default) click on the tickbox to select all the options
- Now click on the "Exchange Rate Settings" tab again
- You will now see that all the currency modules are selected..