Answer
If this is the first invoice posted using that particular foreign currency, check whether the currency code has actually been set up as a Code Part Value yet — currency is typically configured as a code part in the standard chart-of-accounts setup, found under Accounting Rules > Code String > Code Part Values. A currency code that hasn't been added to Code Part Values can cause the posting to not resolve/display the way you'd expect in an account inquiry; adding the missing currency code there is usually what's needed to get postings in that currency to show up correctly going forward.