& & cannot be converted to &

What causes this issue?

You want to translate an amount of &v1& &v2& into &v3&, but no average
rate has been defined for translation for &v4&.

How to fix this error?

Maintain the exchange rate with exchange rate type "M" from &V2& to
&V3& for &V4&.

Error message extract from SAP system. Copyright SAP SE.