Unable to access in customer unpaid invoices the copy to

There is no “New Receipt” option. there is just a small white box appears under the copy to. It is too narrow to event type in

You do not have any bank accounts defined, and your Bank Accounts tab is not enabled. Manager will not display features you cannot use. You also do not have the Receipts & Payments tab enabled.

Read this Guide for general information: https://www.manager.io/guides/7397.
Read this one for more detail: https://www.manager.io/guides/8865.