Migration Wizard not available - trouble importing opening balances from Wave

Migration Wizard not available - trouble importing opening balances from Wave

Hi there,
I have signed up for Zoho book from Wave and initially imported some data (customers, chart of accounts) using the Migration Wizard.
Now I am at the beginning of the new financial year and wanting to import more data such as opening balances. 
The Migration Wizard is no longer available on my profile and so I have been trying to use the "Enter opening balances" page. One of the first things to be imported is the "Accounts receivable" .csv. However, I have not managed to export this from Wave and do not see this anywhere in the Migrate to Zoho from Wave help doc. This document is very detailed but describes the process while using the import wizard.

Any suggestions on how to get the wizard back? Or how to otherwise import this data?

Thanks
Greg