I am using Marketing Cloud Journey Builder to send emails to Contacts when a related Custom Object (via Lookup field) is inserted.
In my Event Source I have select the Salesforce Object and selected all the fields I'd like from the Custom Object and the Contact in the Event Data tab (when selecting Entry Source).
When selecting an email which contains any of the fields i.e FirstName, no matter which tag I use whether it be
%%Contact__r.FirstName%%, when I click Test on the Journey an error is returned because the email fails validation. If I take out any of these tags the test passes so it's definitely the related data.
Can someone tell me what the correct way would be access the related data in my Emails?