There are a number of reasons why contacts might not sync between CRM and Campaigns, including:

* The most common reason is that the contact in CRM does not have an email address associated with it

* If the email address of the contact in CRM already exists on a contact in Campaigns, the system will not sync duplicate email addresses from CRM to Campaigns

* If the contact in CRM has a group email address associated with it (ie info@, support@, admin@ etc) this is considered to be a restricted email address and the system cannot sync these contacts to Campaigns. More information on this can be found on the Zoho website: https://help.zoho.com/portal/kb/articles/what-is-role-group-address

To check why contacts are not syncing between CRM and Campaigns, click into the sync settings in Campaigns (Contacts >> Sync Services >> Active Syncs) and then click on the sync in question. There will be a section called Imported Contacts which shows the details of the contacts, and one of the options is Ignored Contacts. Click on the number of Ignored Contacts to expand on the details, and you will see an option to Export the list of Ignored Contacts to Excel, which will give full information of which contacts have been ignored and why.