We have found a solution and I have been able to test and confirm the solution is working for the issue of new members not being added to a workflow from a synced report. The solution was that a field needed to be added to your report that you are syncing to the New Member list. The field is called "Contactid". I have added the field to your current saved report and have deleted my test membership and contacts. I have a screenshot below of your saved report with the field I added.
*Important note for the future- For new Marketing Automation workflows, the report you are saving and selecting for the workflow must include the "Contactid" field for the dynamic list to update each night.
The Contactid field in a report is a unique id that shows in the URL for a contact while viewing their
Here is the Contactid field when added to a report. You will need to make sure this field is added to any report you would like to save and update a Dynamic List each night.