Can't mark rules in Multiple objects


I’m creating a Purchasing Card system with employee approvals and I’m stuck at one of the last steps in order to get our reports to work successfully.

I have a parent object named “Purchase Order” which is linked to the Purchasing Card User role with a checkbox field named Approve. The Purchase Order object has a child object named Split Sites or Departments with another Approve field. I have another Parent Object named Purchasing Card Statement Upload that has links to both the Purchase Order and Split Sites or Departments objects.

The basic order of operations for the app is that a Purchase Order object record is created first, then records are created under the Split Sites or Departments object which link to the Purchase Order object. At the end of the month a Purchasing Card Admin user role will create a record under the Purchasing Card Statement Upload object and choose which Purchasing Card User to assign it to. The Purchasing Card Users will then see a page displayed asking to sign and approve the statement. This page updates the Purchasing Card Statement Upload object records and allows users to choose which Purchase Order records they would like to assign to the Purchasing Card Statement Upload record. It looks like this:

I have submit record rules on this page that update connected records on Each Purchase Order Connected to this record to Approved Order = Yes and update connected records on Each Split Sites or Department connected to this record = Yes. Which looks like this:

I believe the problem is due to the fact that nothing is referencing the Split Sites or Department on the Purchasing Card Statement object until this page. I was hoping that since the Purchase Order object and Split Sites or Department objects are linked (and referenced before this stage) that the submit rules would work. That doesn’t seem to be the case so I’m wondering if anyone has any other suggestions.

The ultimate end goal is to find a way to update the Approved status to both the Purchase Order object record and the multiple Split Sites or Departments object records that are attached to the Purchase Order object record.

I can share more screenshots of my current project if it helps.