Zoho Invoice - CRM -One integration questions

Zoho Invoice - CRM -One integration questions

I have Zoho Invoice as part of the Zoho One package. Yet it will not let me add users.

1. When in Zoho Invoice > Users & Roles, there is no 'INVITE' option for adding any of the four CRM/Zoho One users. And when I click on the Users tab, I get an internal server error on a page with a long url but that has zoho books in the url. I have emailed support and not received an answer so trying here.

2. When in Zoho Invoice, I am trying to sync 'invoices and estimates' with Zoho CRM. But when I click enable on this feature, it says my CRM Edition does not support this module. That can't be right. Is there a setting I need to enable in CRM?