Yes, now it's clear. You're right, VM invoice currently doesn't support adding downloadable products. We will put it to our task list.

Thanks! Could you perhaps suggest a workaround or something so that customers who bought downloadable products via phone/email can have an access to the downloadable product?

Thanks much!

Only workaround for now is:
1. create order manually from VirtueMart frontend (with your credentials).
2. open order in VM Invoice and assign it to real customer (or create new customer for it). (additional note: virtemart sends that info to user default billing e-mail, not order specific billing e-mail)
3. save order.
4. change status (from VM invoice or Virtuemart) to status you defined in Virtumart for enabling downloads. E-mail should be sent.