Multi-Currency: The multi-currency feature in QBO gives you the ability to record transactions in foreign currencies. If you have customers, suppliers, or bank accounts that use a currency other than your local currency, you can turn on the multi-currency feature to properly track these transactions. As well as exchange rate gains and losses.
Warning: Once multi-currency is enabled in QBO it can NOT be turned off.
Once you have multi-currency turned on in QBO. You will then want to enable this in Mobius.
To this go to Set Up Quickbooks online > Select your company > Currency > Enable "Multi-Currency" > Click save.