Can 'Request an Update' work with a Formula-derived Contact List?

Hi folks--We have a business process where, depending on a field value, I want an automation to send a Request an Update to either the staff in one department, or the staff in another.

I set up a satellite sheet with a list of staff. "Name" is a contact list column, "Email" is just text/number:

In the primary sheet, I have a contact list field ("MP Contacts") that uses a Join/Collect formula to grab the aggregate info from a specific department.

The formula works fine, but the Automation I've created to use the data in that field is not working. I've tried using both "Name" and "Email" in the formula with no luck.

I've made other Automations that have worked fine when a contact field just contains an email address. The aggregate emails seem to be formatted correctly (this is using "EMail" in the formula):

I'm at a loss. Thoughts?