I want to replace an existing user in Zoho Campaigns and Survey in CRM Plus with a new user account. When I try to delete the existing user and add a new one in the respective applications, I get a message "Oops, you've used up all your purchased user licenses." What could be the reason?

I want to replace an existing user in Zoho Campaigns and Survey in CRM Plus with a new user account. When I try to delete the existing user and add a new one in the respective applications, I get a message "Oops, you've used up all your purchased user licenses." What could be the reason?

You are trying to deactivate your existing user only from Campaigns and Survey and not entirely from CRM Plus. So the user is still active in CRM Plus. Only the service access has been denied to this user.
 
When you try to create a new user account in Campaigns and Survey, it will be considered as a new user license in CRM Plus. If the number of user licenses you have purchased is less, you will get a message that you have used up all your user licenses. If you are a CRM Plus Admin, you can purchase an additional user license in order to add this new user.