Flow Designer - Unable to Create REQ/RITM from Inbound Email for External Guest User

[PaluriK]

Requirement:

When an email is received from an external guest user (the sender does not exist in the sys_user table), the flow should create a REQ and RITM successfully.

Working as expected with the users exist in the sys_user table and REQ/RITM is created successfully. 

Current Setup:

- Flow Trigger: Inbound Email

- The flow is triggered successfully.

- Catalog variables are populated.

- Requester email is stored as a String variable (not a reference).

- The sender is an external email address and does not exist in sys_user.

Issue:

The flow reaches the catalog request creation step but fails while creating the REQ/RITM. The execution shows a cart-related error attached the screenshot, and no REQ or RITM is created.

Can anyone help me on this issue if the Create Catalog Request action require a valid sys_user record even if the requester email is stored as a String?

2. Is there any supported approach to create a REQ/RITM for external users who are not present in the sys_user table?

3. Is there any additional configuration required for the Cart API or guest users?

Kindly let me know if you need any further details. I will be happy to share as soon as possible.