I appreciate you for raising your concerns here, @salimdk.
I recognize you'd like to utilize this multicurrency feature in QuickBooks Online.
We need to turn on the multicurrency feature before we can use specific rates within your transaction. If you haven't turned this on yet, I've got you this article for the detailed steps: Turn on and use multicurrency in QuickBooks Online.
However, If you're still having the same error, may I ask for a screenshot of the transaction you've made? This way, I'd be able to provide the exact solution to this matter.
I'll be waiting for your reply. Have a good one.
