Invoice not emailed; Cancel & Create buttons not showing

We have had this plugin installed for some years now. The workflow was as follows:

A customer would place an order using Bacs as the payment method. The order would go On Hold and the order information and invoice would be emailed to the customer. The customer would then secure a Purchase Order number from their company, which we would add to the order notes.

We would click Cancel on the invoice section, then Create to regenerate it. This would add the Purchase Order number to the invoice as order notes. Then we would select Resend Invoice from the dropdown.

Recently it has been brought to my attention that the following issues now exist:

1. The invoice does not get emailed when the order goes On Hold.
2. The Cancel and Create buttons are absent.
3. The option to Resend Invoice no longer exists.

Were these features removed or have we bugs in our system?