Error when trying to generate record action (step-by-step #5)

Hi there,

I'm on the last part of the instructions where we have to create a record action:

1. In the left menu, go to the Actions page.
2. Click GENERATE RECORD ACTIONS.
3. In the Choose Your Action dialog, deselect Update and Delete. For this exercise, you will focus on the Create record action. Click CUSTOMIZE.
4. Configure the following properties:
● Display Name: Enter Add Vehicle.
● Description: Enter Action to add a new vehicle to the fleet.
● Click NEXT: REVIEW OBJECTS.
5. Review the objects that Appian generates for this action, including a process model and interface for adding a new vehicle.
6. Click GENERATE.

After clicking GENERATE in step 6, I am put back at the Actions page with the following error displayed (Your record actions and supporting objects could not be created. Try generating them again or configuring manually.):

Interestingly, when I look at the object listing for the site, I see that the Process Model was generated, but not the Interface:

Any suggestions on how I can move past this?

Thank you,
Stefan.