Placeholder Value Not Working

What notification template part did you add this to?  Are you sure that the placeholder template is correct (your example seems to be missing a closing percent sign)?

Hi Craig.

I added it to the Notification Templates\Email Templates section.

From the Email Templates, I click on the gear icon (circled below)

Then there's a button to insert the placeholder

When I click on 'Insert Placeholder' button, it allows me to select the property/placeholder and it put it between brackets {}.

I select the property/placeholder as part of the text notification.

This is what shows up as part of the email subject instead of the actual property.

I get the same results when I put placeholders in the email message.

I had issue in the past, if the alias has a space in the name, it is not working correctly.

The aliases/placeholders I am using are single word and has no spaces.

The template section you're editing is the digest summary.  The digest summary isn't something which is used per-object (it's a digest; it typically represents multiple objects).  Whilst this isn't explicitly documented anywhere I can find (I quickly checked the user guide and the actual AVS section), my suspicion is that you simply cannot use this placeholder in this section as it doesn't make sense.

Have you tried in other notifications which have a specific object context, and have you tried in both subject and body sections of those?

It seems that only the built-in properties/placeholders such as NameAndLinksHtml() work with the notifications

I am not sure that's entirely correct, but there is a list of items on the user guide: Personalizing Notification Messages (m-files.com)

That states "in addition to the object properties", so my assumption is that property data should also work in appropriate templates.

I see now where the properties should be mapped additionally.  There's a reference button that allows you to map the placeholders to the actual property IDs.