I believe we can do it using a content template. Check this article about the item attribute. We can use a content template and pass it the item attribute as "%%POST_ID%%" and inside of that content template, we can pass the parent post to the item attribute.
Considering that the relationship's slug is "my-parent-my-child" we can create a content template "my-get-arrival-time". The content template will have:
[types field="arrival-time" item="@my-parent-my-child.parent"]
And we'll use the content template inside of the notification using:
[wpv-post-body template="my-get-arrival-time" item="%%POST_ID%%"]
Please try it and if it does not work, I'll check on a clean install if this is a bug and will discuss it with our 2nd Tier to confirm.
Still not working I'm afraid.
We are also expecting the notifications to be sent 1 day before the event date, but they are going a week before instead.
I run a test locally and I was able to display the arrival date from the offer post with the following:
- New content template(slug: opportunity-arrival-date-for-reminder-notification) with the following code:
[types field='arrival-time' item="@opportunity-offer.parent"][/types]
I included it in the notification with:
[wpv-post-body view_template="opportunity-arrival-date-for-reminder-notification" item="%%POST_ID%%"]
Please create a content template and adapt the code to your template slug.
Regarding the issue in your last reply, I have created another ticket for it. For support rules, we are able to handle only one issue at a time. This helps us to bring you a better service and also helps other users to find all the information here exposed.