Zoho Books is a Caddi-managed connector. There is no Zoho API Console application to create and nothing for an administrator to configure — you sign in to Zoho and approve Caddi.
A connection is bound to one Zoho Books organization. Every Zoho Books API call names an organization, so Caddi picks one when you connect: your default organization, or the first one listed if none is marked default. If you keep books for several entities, check that the right one is your Zoho default before connecting.
Before you start
You'll need:
A Zoho account with access to the Zoho Books organization you want to connect
A Caddi account
Step 1: Connect your account
In Caddi, open Settings, then Integrations, and go to the My Connections tab.
Find Zoho Books and click Connect +.
Sign in to Zoho.
Review the permissions on Zoho's consent screen and click Accept.
You'll be returned to Caddi. Caddi looks up your Zoho Books organizations and binds the connection to one of them.
How the connection behaves
The connection shows which organization it works in, so you can see which set of books a loop is acting on.
Zoho's settings-read permission is always part of the grant. Caddi uses it to find your organization.
Access tokens last an hour and are renewed in the background. Zoho refresh tokens stay valid until revoked, so the connection continues to renew without action from you.
Zoho asks for consent every time you connect, even if you have approved Caddi before.
Troubleshooting
Connecting fails saying the account has no Zoho Books organization
The Zoho account you signed in with is not a member of any Zoho Books organization. Sign in with an account that is, or have an administrator add you.
Caddi is working in the wrong set of books
Caddi used your Zoho default organization. Change the default in Zoho Books, then disconnect and reconnect in Caddi.
Creating invoices or contacts fails
The permissions granted at sign-in were narrower than the loop needs. Disconnect, reconnect, and approve the full request.
Sign-in succeeds but Zoho rejects the token afterwards
Zoho runs separate data centres (zoho.com, zoho.eu, zoho.in, zoho.com.au and others) and a token issued in one is not valid in another. If your Zoho account is in a different data centre, contact Caddi support.
Still stuck? Contact Caddi support with the exact error message you're seeing and the time it occurred.
Sources
OAuth 2.0 — Zoho Books API docs
Authorization request — Zoho Accounts OAuth docs