What is an Org?
An org is an organization registered with Zoho. Let's say you own a company named Zylker. Once you register it with Zoho, Zylker is treated as an Org and can have multiple users associated with it. However, a person can belong to only one Zoho org at a time. When you invite someone who is already a member of another org, you will receive the following message: "Invite to the user failed as the person is already a member of another org."
Example: If you invite a person from another organization called Pymtech, to the Zylker network, then the invite cannot be processed.
How to invite a user who already belongs to a different Org?
The user would have to delete their existing org or contact their org admin and remove themselves from the org, and then join your network. You can send them the invites along with the steps to remove themselves from their org.
Invite failure due to mismatch of data centers
The invite will fail if the invited user has an existing Zoho account in a different data center. This is because an individual user account and the network to which the person is invited should be associated with the same data center.
Example: If your network is a part of the US set up and the person you are inviting has a Zoho account is in the EU set up, then the invite would fail.
How to invite users from a different data center?
The user should delete their existing Zoho account and create a new one in the set up corresponding to the network they are invited to.
In the above-said example case, the user should delete their existing account that is in the EU setup and create a new account in the US set up, and then accept the invite to join the network.