Advanced currency management (ACM) is an optional Salesforce functionality that must be enabled directly by Salesforce, to allow you to manage dated exchange rates on opportunity records.

When ACM is enabled in your org and being used on opportunities, you cannot use any Currency data typed opportunity object fields in your intelligent approval emails or on the approval summary page. This includes the standard Amount field and any custom fields using the currency type.

To have currency type field information in your emails, you cannot have the values within the content of the email. You must link back to the opportunity record itself in the email for users to view the data in Salesforce.