Currently, we have an ongoing issue about customers getting this error in QuickBooks Online.
As a workaround, you can create a holding account in the home currency. You can use the holding account instead of the foreign currency bank. Then, create a transfer between the bank and the holding account
You can contact our QuickBooks Technical Team so they can add your company details to the list of affected users. You can them via chat or email.
Please feel free to come back to the Community if you have other questions. I'm here to help.