When editing a merge mapping I'm unable to add a new salesforce custom field as a source value

When editing a (or creating a new) Merge Mapping I can't seem to find any of the new custom fields I created a few days ago in salesforce under an existing custom object. I was able to find the custom object as a reference easily enough within the Source Value popup menu (Object Selector) on the Merge Mapping tab as well as all the old fields under that object just not this set of new fields I created.

For what it's worth, these fields are all formula fields and are read-only accessible by all profiles in salesforce.

It feels as if there's something I need to do in order to refresh this list within Object Selector, but I can't seem to find any mention of how to do so in any of the documentation I've found, mainly this tutorial and this knowledge article:

Salesforce Integration: https://helpx.adobe.com/sign/how-to/adobe-salesforce-integration.html
Adobe Sign for Salesforce - Field Mapping and Templates: https://helpx.adobe.com/in/sign/using/salesforce-data-mapping-templates.html

Any insights on this would be greatly appreciated!